properly handle fat pointers to uninhabitable types

Calculate the pointee metadata size by using `tcx.struct_tail_erasing_lifetimes` instead of duplicating the logic in `fat_pointer_kind`. Open to alternatively suggestions on how to fix this.

Fixes #94149

r? ````@michaelwoerister```` since you touched this code last, I think!

Stop manually SIMDing in `swap_nonoverlapping`

Like I previously did for `reverse` (#90821), this leaves it to LLVM to pick how to vectorize it, since it can know better the chunk size to use, compared to the "32 bytes always" approach we currently have.

A variety of codegen tests are included to confirm that the various cases are still being vectorized.

It does still need logic to type-erase in some cases, though, as while LLVM is now smart enough to vectorize over slices of things like `[u8; 4]`, it fails to do so over slices of `[u8; 3]`.

As a bonus, this change also means one no longer gets the spurious `memcpy`(s?) at the end up swapping a slice of `__m256`s: <https://rust.godbolt.org/z/joofr4v8Y>

<details>

<summary>ASM for this example</summary>

## Before (from godbolt)

note the `push`/`pop`s and `memcpy`

```x86
swap_m256_slice:
        push    r15
        push    r14
        push    r13
        push    r12
        push    rbx
        sub     rsp, 32
        cmp     rsi, rcx
        jne     .LBB0_6
        mov     r14, rsi
        shl     r14, 5
        je      .LBB0_6
        mov     r15, rdx
        mov     rbx, rdi
        xor     eax, eax
.LBB0_3:
        mov     rcx, rax
        vmovaps ymm0, ymmword ptr [rbx + rax]
        vmovaps ymm1, ymmword ptr [r15 + rax]
        vmovaps ymmword ptr [rbx + rax], ymm1
        vmovaps ymmword ptr [r15 + rax], ymm0
        add     rax, 32
        add     rcx, 64
        cmp     rcx, r14
        jbe     .LBB0_3
        sub     r14, rax
        jbe     .LBB0_6
        add     rbx, rax
        add     r15, rax
        mov     r12, rsp
        mov     r13, qword ptr [rip + memcpy@GOTPCREL]
        mov     rdi, r12
        mov     rsi, rbx
        mov     rdx, r14
        vzeroupper
        call    r13
        mov     rdi, rbx
        mov     rsi, r15
        mov     rdx, r14
        call    r13
        mov     rdi, r15
        mov     rsi, r12
        mov     rdx, r14
        call    r13
.LBB0_6:
        add     rsp, 32
        pop     rbx
        pop     r12
        pop     r13
        pop     r14
        pop     r15
        vzeroupper
        ret
```

## After (from my machine)

Note no `rsp` manipulation, sorry for different ASM syntax

```x86
swap_m256_slice:
	cmpq	%r9, %rdx
	jne	.LBB1_6
	testq	%rdx, %rdx
	je	.LBB1_6
	cmpq	$1, %rdx
	jne	.LBB1_7
	xorl	%r10d, %r10d
	jmp	.LBB1_4
.LBB1_7:
	movq	%rdx, %r9
	andq	$-2, %r9
	movl	$32, %eax
	xorl	%r10d, %r10d
	.p2align	4, 0x90
.LBB1_8:
	vmovaps	-32(%rcx,%rax), %ymm0
	vmovaps	-32(%r8,%rax), %ymm1
	vmovaps	%ymm1, -32(%rcx,%rax)
	vmovaps	%ymm0, -32(%r8,%rax)
	vmovaps	(%rcx,%rax), %ymm0
	vmovaps	(%r8,%rax), %ymm1
	vmovaps	%ymm1, (%rcx,%rax)
	vmovaps	%ymm0, (%r8,%rax)
	addq	$2, %r10
	addq	$64, %rax
	cmpq	%r10, %r9
	jne	.LBB1_8
.LBB1_4:
	testb	$1, %dl
	je	.LBB1_6
	shlq	$5, %r10
	vmovaps	(%rcx,%r10), %ymm0
	vmovaps	(%r8,%r10), %ymm1
	vmovaps	%ymm1, (%rcx,%r10)
	vmovaps	%ymm0, (%r8,%r10)
.LBB1_6:
	vzeroupper
	retq
```

</details>

This does all its copying operations as either the original type or as `MaybeUninit`s, so as far as I know there should be no potential abstract machine issues with reading padding bytes as integers.

<details>

<summary>Perf is essentially unchanged</summary>

Though perhaps with more target features this would help more, if it could pick bigger chunks

## Before

```
running 10 tests
test slice::swap_with_slice_4x_usize_30                            ... bench:         894 ns/iter (+/- 11)
test slice::swap_with_slice_4x_usize_3000                          ... bench:      99,476 ns/iter (+/- 2,784)
test slice::swap_with_slice_5x_usize_30                            ... bench:       1,257 ns/iter (+/- 7)
test slice::swap_with_slice_5x_usize_3000                          ... bench:     139,922 ns/iter (+/- 959)
test slice::swap_with_slice_rgb_30                                 ... bench:         328 ns/iter (+/- 27)
test slice::swap_with_slice_rgb_3000                               ... bench:      16,215 ns/iter (+/- 176)
test slice::swap_with_slice_u8_30                                  ... bench:         312 ns/iter (+/- 9)
test slice::swap_with_slice_u8_3000                                ... bench:       5,401 ns/iter (+/- 123)
test slice::swap_with_slice_usize_30                               ... bench:         368 ns/iter (+/- 3)
test slice::swap_with_slice_usize_3000                             ... bench:      28,472 ns/iter (+/- 3,913)
```

## After

```
running 10 tests
test slice::swap_with_slice_4x_usize_30                            ... bench:         868 ns/iter (+/- 36)
test slice::swap_with_slice_4x_usize_3000                          ... bench:      99,642 ns/iter (+/- 1,507)
test slice::swap_with_slice_5x_usize_30                            ... bench:       1,194 ns/iter (+/- 11)
test slice::swap_with_slice_5x_usize_3000                          ... bench:     139,761 ns/iter (+/- 5,018)
test slice::swap_with_slice_rgb_30                                 ... bench:         324 ns/iter (+/- 6)
test slice::swap_with_slice_rgb_3000                               ... bench:      15,962 ns/iter (+/- 287)
test slice::swap_with_slice_u8_30                                  ... bench:         281 ns/iter (+/- 5)
test slice::swap_with_slice_u8_3000                                ... bench:       5,324 ns/iter (+/- 40)
test slice::swap_with_slice_usize_30                               ... bench:         275 ns/iter (+/- 5)
test slice::swap_with_slice_usize_3000                             ... bench:      28,277 ns/iter (+/- 277)
```

</detail>

Improve `--check-cfg` implementation

This pull-request is a mix of improvements regarding the `--check-cfg` implementation:

- Simpler internal representation (usage of `Option` instead of separate bool)
- Add --check-cfg to the unstable book (based on the RFC)
- Improved diagnostics:
    * List possible values when the value is unexpected
    * Suggest if possible a name or value that is similar
- Add more tests (well known names, mix of combinations, ...)

r? ```@petrochenkov```

better ObligationCause for normalization errors in `can_type_implement_copy`

Some logic is needed so we can point to the field when given totally nonsense types like `struct Foo(<u32 as Iterator>::Item);`

Fixes #93687

resolve/metadata: Stop encoding macros as reexports

Supersedes https://github.com/rust-lang/rust/pull/88335.
r? `@cjgillot`

To make the `macro_rules` flag more readily available without decoding everything else

Previously it always returned `MacroKind::Bang` while some of those macros are actually attributes and derives

Always format to internal String in FmtPrinter

This avoids monomorphizing for different parameters, decreasing generic code
instantiated downstream from rustc_middle -- locally seeing 7% unoptimized LLVM IR
line wins on rustc_borrowck, for example.

We likely can't/shouldn't get rid of the Result-ness on most functions, though some
further cleanup avoiding fmt::Error where we now know it won't occur may be possible,
though somewhat painful -- fmt::Write is a pretty annoying API to work with in practice
when you're trying to use it infallibly.

Partially move cg_ssa towards using a single builder

Not all codegen backends can handle hopping between blocks well. For example Cranelift requires blocks to be terminated before switching to building a new block. Rust-gpu requires a `RefCell` to allow hopping between blocks and cg_gcc currently has a buggy implementation of hopping between blocks. This PR reduces the amount of cases where cg_ssa switches between blocks before they are finished and mostly fixes the block hopping in cg_gcc. (~~only `scalar_to_backend` doesn't handle it correctly yet in cg_gcc~~ fixed that one.)

`@antoyo` please review the cg_gcc changes.

Back more metadata using per-query tables

r? `@ghost`

Rollup of 9 pull requests

Successful merges:

 - #89887 (Change `char` type in debuginfo to DW_ATE_UTF)
 - #94267 (Remove unused ordering derivations and bounds for `SimplifiedTypeGen`)
 - #94270 (Miri: relax fn ptr check)
 - #94273 (add matching doc to errorkind)
 - #94283 (remove feature gate in control_flow examples)
 - #94288 (Cleanup a few Decoder methods)
 - #94292 (riscv32imc_esp_espidf: set max_atomic_width to 64)
 - #94296 (⬆ rust-analyzer)
 - #94300 (Fix a typo in documentation of `array::IntoIter::new_unchecked`)

Failed merges:

r? `@ghost`
`@rustbot` modify labels: rollup

Fix a typo in documentation of `array::IntoIter::new_unchecked`

🌸

⬆ rust-analyzer

r? `@ghost`

riscv32imc_esp_espidf: set max_atomic_width to 64

For espidf targets without native atomics, there is atomic emulation inside [the newlib component of espidf](https://github.com/espressif/esp-idf/blob/master/components/newlib/stdatomic.c), this has been extended to support emulation up to 64bits therefore we are safe to increase the atomic width for the `riscv32imc_esp_espidf` target.

Closes https://github.com/esp-rs/rust/issues/107

cc: `@ivmarkov`

Cleanup a few Decoder methods

This is just some simple follow up to #93839.

r? `@nnethercote`

remove feature gate in control_flow examples

Stabilization was done in https://github.com/rust-lang/rust/pull/91091, but the two examples weren't updated accordingly.

Probably too late to put it into stable, but it should be in the next release :)

add matching doc to errorkind

Rework of #90706

Miri: relax fn ptr check

As discussed in https://github.com/rust-lang/unsafe-code-guidelines/issues/72#issuecomment-1025407536, the function pointer check done by Miri is currently overeager: contrary to our usual principle of only checking rather uncontroversial validity invariants, we actually check that the pointer points to a real function.

So, this relaxes the check to what the validity invariant probably will be (and what the reference already says it is): the function pointer must be non-null, and that's it.

The check that CTFE does on the final value of a constant is unchanged -- CTFE recurses through references, so it makes some sense to also recurse through function pointers. We might still want to relax this in the future, but that would be a separate change.

r? `@oli-obk`

Remove unused ordering derivations and bounds for `SimplifiedTypeGen`

This is another small PR clearing the way for work on #90317.

Change `char` type in debuginfo to DW_ATE_UTF

Rust previously encoded the `char` type as DW_ATE_unsigned_char. The more appropriate encoding is `DW_ATE_UTF`.

Clang also uses the DW_ATE_UTF for `char32_t` in C++.

This fixes the display of the `char` type in the Windows debuggers. Without this change, the variable did not show in the locals window.
![image](https://user-images.githubusercontent.com/704597/137368067-9b3e4dc8-a075-44ba-a687-bf3810a44e5a.png)

LLDB 13 is also able to display the char value, when before it failed with `need to add support for DW_TAG_base_type 'char' encoded with DW_ATE = 0x8, bit_size = 32`

r? `@wesleywiser`

Reapply cg_llvm: `fewer_names` in `uncached_llvm_type`

r? `@davidtwco` `@erikdesjardins`

Node id to hir id refactor

Related to #89278

r? `@oli-obk`

Co-authored-by: NJosh Triplett <josh@joshtriplett.org>

Rollup of 12 pull requests

Successful merges:

 - #94128 (rustdoc: several minor fixes)
 - #94137 (rustdoc-json: Better Header Type)
 - #94213 (fix names in feature(...) suggestion)
 - #94240 (Suggest calling .display() on `PathBuf` too)
 - #94253 (Use 2021 edition in ./x.py fmt)
 - #94259 (Bump download-ci-llvm-stamp for llvm-nm inclusion)
 - #94260 (Fix rustdoc infinite redirection generation)
 - #94263 (Typo fix: Close inline-code backtick)
 - #94264 (Fix typo.)
 - #94271 (Miri: extend comments on downcast operation)
 - #94280 (Rename `region_should_not_be_omitted` to `should_print_region`)
 - #94285 (Sync rustc_codegen_cranelift)

Failed merges:

r? `@ghost`
`@rustbot` modify labels: rollup

Rust previously encoded the `char` type as DW_ATE_unsigned_char. The more
appropriate encoding is DW_ATE_UTF.

Clang uses this same debug encoding for char32_t.

This fixes the display of `char` types in Windows debuggers as well as LLDB.

- Test the combinations of --check-cfg with partial values() and --cfg
- Test that we detect unexpected value when none are expected

Sync rustc_codegen_cranelift

r? `@ghost`

`@rustbot` label +A-codegen +A-cranelift +T-compiler