Do not accidentally treat multi-segment meta-items as single-segment

Fixes https://github.com/rust-lang/rust/issues/55168 and many other regressions from https://github.com/rust-lang/rust/pull/50030

Basically, attributes like `#[any::prefix::foo]` were commonly interpreted as `#[foo]` due to `name()` successfully returning the last segment (this applies to nested things as well `#[attr(any::prefix::foo)]`).

Remove methods `Attribute::span` and `MetaItem::span` duplicating public fields

Tweak some error wording

Rollup of 37 pull requests

Successful merges:

 - #58854 (appveyor: Use VS2017 for all our images)
 - #58855 (std: Spin for a global malloc lock on wasm32)
 - #58873 (Fix "Auto-hide item methods documentation" setting)
 - #58901 (Change `std::fs::copy` to use `copyfile` on MacOS and iOS)
 - #58933 (Move alloc::prelude::* to alloc::prelude::v1, make alloc a subset of std)
 - #58938 (core: ensure VaList passes improper_ctypes lint)
 - #58941 (MIPS: add r6 support)
 - #58949 (SGX target: Expose thread id function in os module)
 - #58959 (Add release notes for PR #56243)
 - #58976 (Default to integrated `rust-lld` linker for UEFI targets)
 - #59009 (Fix SGX implementations of read/write_vectored.)
 - #59025 (Fix generic argument lookup for Self)
 - #59036 (Fix ICE in MIR pretty printing)
 - #59037 (Avoid some common false positives in intra doc link checking)
 - #59072 (we can now skip should_panic tests with the libtest harness)
 - #59079 (add suggestions to invalid macro item error)
 - #59082 (A few improvements to comments in user-facing crates)
 - #59102 (Consistent naming for duration_float methods and additional f32 methods)
 - #59118 (rustc: fix ICE when trait alias has bare Self)
 - #59139 (Unregress using scalar unions in constants.)
 - #59146 (Suggest return lifetime when there's only one named lifetime)
 - #59147 (Make std time tests more robust for platform differences)
 - #59152 (Stabilize Range*::contains.)
 - #59156 ([wg-async-await] Add regression test for #55809.)
 - #59158 (Revert "Don't generate minification variable if minification disabled")
 - #59169 (Add `-Z allow_features=...` flag)
 - #59173 (bootstrap: Default to a sensible llvm-suffix.)
 - #59175 (Don't run test launching `echo` since that doesn't exist on Windows)
 - #59180 (Use try blocks in rustc_codegen_ssa)
 - #59185 (No old chestnuts in iter::repeat docs)
 - #59201 (Remove restriction on isize/usize in repr(simd))
 - #59204 (Output diagnostic information for rustdoc)
 - #59206 (Improved test output)
 - #59208 (Reduce a Code Repetition Related to Bit Operation)
 - #59212 (Add x86_64 musl host to the manifest)
 - #59221 (Option and Result: Add references to documentation of as_ref and as_mut)
 - #59231 (Stabilize Option::copied)

Stabilize Option::copied

closes https://github.com/rust-lang/rust/issues/57126

Add release notes for PR #56243

Fixes #58907

Option and Result: Add references to documentation of as_ref and as_mut

This makes the documentation more consistent with that of `Pin::as_ref` which converts "from `&Pin<Pointer<T>>` to `Pin<&t>`".

This generally makes it clearer that the reference is going inside the option.

Add x86_64 musl host to the manifest

@alexcrichton r?

Probably too late for https://github.com/rust-lang/rust/pull/59207

Reduce a Code Repetition Related to Bit Operation

This PR is related to [#49937](https://github.com/rust-lang/rust/issues/49937).
Should I do more commits about [`FIXME(49937)`](https://github.com/rust-lang/rust/search?q=FIXME%2849937%29&unscoped_q=FIXME%2849937%29) in this PR?

Improved test output

Output diagnostic information for rustdoc

Use the information same as rustc.

Remove restriction on isize/usize in repr(simd)

As discussed in #55078, there's no known reason for this restriction.

It's unlikely that repr(simd) will be stabilized in its current form, but
might as well remove some restrictions on it.

This removes the branch in `is_machine` which returns false for these types.
`is_machine` is only used for the repr(simd) type validation check.

No old chestnuts in iter::repeat docs

The current language may be amusing, yet is just imprecise and most especially difficult to understand for someone who speaks English as a foreign language.

Use try blocks in rustc_codegen_ssa

r? @scottmcm

Don't run test launching `echo` since that doesn't exist on Windows

bootstrap: Default to a sensible llvm-suffix.

I used version-channel-sha, hopefully that should work.

I checked that bootstrap builds, but I cannot check anything else since the llvm
build process is started from cargo, and thus calls clang, and thus I hit the
same bug I hope to fix with this change.

Hopefully fixes #59034.

Add `-Z allow_features=...` flag

Adds a compiler option to allow only whitelisted features.

For projects on nightly that want to prevent feature-creep (and maybe, someday, move off of nightly). Not being able to enforce this has been a problem on Fuchsia and at other big companies.

This doesn't support filtering edition feature flags, but someone is welcome to add that if they need it.

Revert "Don't generate minification variable if minification disabled"

Reverts #58643

Fixes #59157

https://github.com/rust-lang/rust/pull/58643 made us stop generating minification variables when minification is disabled, however they may still be needed for parent crates that were generated with minification (this will always be the case for libstd and libcore)

r? @QuietMisdreavus @GuillaumeGomez

[wg-async-await] Add regression test for #55809.

Fixes #55809.

This PR adds a regression test for #55809 which checks that a
overflow does not occur when evaluating a requirement for async
functions and `&mut` arguments in some specific circumstances.

Stabilize Range*::contains.

Closes https://github.com/rust-lang/rust/issues/32311. There's also a bit of rustfmt on range.rs thrown in for good measure (I forgot to turn off format-on-save in VSCode).

Make std time tests more robust for platform differences

Previously, `time::tests::since_epoch` and `time::tests::system_time_math` would fail if the platform represents a SystemTime as unix epoch + `u64` nanoseconds.

r? @sfackler

Suggest return lifetime when there's only one named lifetime

Fix #29094.

Unregress using scalar unions in constants.

fixes https://github.com/rust-lang/rust/issues/59126

r? @RalfJung

I also made a bunch of these invariants panic instead of report an error.

rustc: fix ICE when trait alias has bare Self

Fixes https://github.com/rust-lang/rust/issues/59029

Consistent naming for duration_float methods and additional f32 methods

`duration_float` tracking issue: #54361

New list of methods:
- `as_secs_f64(&self) -> f64`
- `as_secs_f32(&self) -> f32`
- `from_secs_f64(secs: f64) -> Duration`
- `from_secs_f32(secs: f32) -> Duration`
- `mul_f64(self, rhs: f64) -> Duration`
- `mul_f32(self, rhs: f32) -> Duration`
- `div_f64(self, rhs: f64) -> Duration`
- `div_f32(self, rhs: f64) -> Duration`
- `div_duration_f64(self, rhs: Duration) -> f64`
- `div_duration_f32(self, rhs: Duration) -> f32`

With [`num_traits::Float`](https://docs.rs/num-traits/0.2.6/num_traits/float/trait.Float.html) we could've reduced number of methods by factor of two, but unfortunately it's not part of `std`.

A few improvements to comments in user-facing crates

Not too many this time, and all concern comments (almost all doc comments) in user-facing crates (libstd, libcore, liballoc).

r? @steveklabnik

add suggestions to invalid macro item error

r? @estebank

we can now skip should_panic tests with the libtest harness

Avoid some common false positives in intra doc link checking

The empty string case is never going to be a link. The numeric case may be a link, but if it were it would have resolved locally. It's more likely the makeshift markdown footnote notation (`[0]`, etc)

r? @QuietMisdreavus

Fix ICE in MIR pretty printing

A `Def::Variant` should be considered as a function in mir pretty
printing. Each variant has a constructor that we must print.

Given the following enum definition:

```rust
pub enum TestMe {
    X(usize),
}
```

We will need to generate a constructor for the variant `X` with a
signature that looks something like the following:

```
fn TestMe::X(_1: usize) -> TestMe;
```

Fixes: #59021

Fix generic argument lookup for Self

Rewrite the SelfCtor early and use the replacement Def when
calculating the path_segs.

Note that this also changes which def is seen by the code that
computes user_self_ty and is_alias_variant_ctor; I don't see a
immediate issue with that, but I'm not 100% clear on the
implications.

Fixes #57924

r? @EddyB

Fix SGX implementations of read/write_vectored.

closes https://github.com/rust-lang/rust/issues/57126