Fix suggestions for missing return type lifetime specifiers

This pull request aims to fix #84592. The issue is that the current code seems to assume that there is only a single relevant span pointing to the missing lifetime, and only looks at the first one:
https://github.com/rust-lang/rust/blob/e5f83d24aee866a14753a7cedbb4e301dfe5bef5/compiler/rustc_resolve/src/late/lifetimes.rs#L2959

This is incorrect, though, and leads to incorrect error messages and invalid suggestions. For instance, the example from #84592:
```rust
struct TwoLifetimes<'x, 'y> {
    x: &'x (),
    y: &'y (),
}

fn two_lifetimes_needed(a: &(), b: &()) -> TwoLifetimes<'_, '_> {
    TwoLifetimes { x: &(), y: &() }
}
```
currently leads to:
```
error[E0106]: missing lifetime specifiers
 --> src/main.rs:6:57
  |
6 | fn two_lifetimes_needed(a: &(), b: &()) -> TwoLifetimes<'_, '_> {
  |                            ---     ---                  ^^ expected 2 lifetime parameters
  |
  = help: this function's return type contains a borrowed value, but the signature does not say whether it is borrowed from `a` or `b`
help: consider introducing a named lifetime parameter
  |
6 | fn two_lifetimes_needed<'a>(a: &'a (), b: &'a ()) -> TwoLifetimes<'_<'a, 'a>, '_> {
  |                        ^^^^    ^^^^^^     ^^^^^^                  ^^^^^^^^^^
```
There are two problems:
- The error message is wrong. There is only _one_ lifetime parameter expected at the location pointed to by the error message (and another one at a separate location).
- The suggestion is incorrect and will not lead to correct code.

With the changes in this PR, I get the following output:
```
error[E0106]: missing lifetime specifiers
 --> p.rs:6:57
  |
6 | fn two_lifetimes_needed(a: &(), b: &()) -> TwoLifetimes<'_, '_> {
  |                            ---     ---                  ^^  ^^ expected named lifetime parameter
  |                                                         |
  |                                                         expected named lifetime parameter
  |
  = help: this function's return type contains a borrowed value, but the signature does not say whether it is borrowed from `a` or `b`
help: consider introducing a named lifetime parameter
  |
6 | fn two_lifetimes_needed<'a>(a: &'a (), b: &'a ()) -> TwoLifetimes<'a, 'a> {
  |                        ^^^^    ^^^^^^     ^^^^^^                  ^^  ^^

error: aborting due to previous error

For more information about this error, try `rustc --explain E0106`.
```
Mainly, I changed `add_missing_lifetime_specifiers_label()` to receive a _vector_ of spans (and counts) instead of just one, and adjusted its body accordingly.

Fix duplicate unknown lint errors

Fixes rust-lang/rust-clippy#6602

Fix typo

Migrate top doc and non-exhaustive toggles to details tag

Fixes #83332.

r? `@jsha`

Add primary marker on codegen unit and generate main wrapper on primary codegen.

This is the codegen part of changes extracted from #84062.

This add a marker called `primary` on each codegen units, where exactly one codegen unit will be `primary = true` at a time. This specific codegen unit will take charge of generating `main` wrapper when `main` is imported from a foreign crate after the implementation of RFC 1260.

cc #28937

I'm not sure who should i ask for review for codegen changes, so feel free to reassign.
r? `@nagisa`

Add default search path to `Target::search()`

The function `Target::search()` accepts a target triple and returns a `Target` struct defining the requested target.

There is a `// FIXME 16351: add a sane default search path?` comment that indicates it is desirable to include some sort of default. This was raised in https://github.com/rust-lang/rust/issues/16351 which was closed without any resolution.

https://github.com/rust-lang/rust/pull/31117 was proposed, however that has platform-specific logic that is unsuitable for systems without `/etc/`.

This patch implements the suggestion raised in https://github.com/rust-lang/rust/issues/16351#issuecomment-180878193 where a `target.json` file may be placed in `$(rustc --print sysroot)/lib/rustlib/<target-triple>/target.json`. This allows shipping a toolchain distribution as a single file that gets extracted to the sysroot.

Avoid predecessors having Drop impls

Should be a simple win - but let's make sure with perf.

Improve support for NewPM

This adds various missing bits of support for NewPM and allows us to successfully run stage 2 tests with NewPM enabled.

This does not yet enable NewPM by default, as there are still known issue on LLVM 12 (such as a weak fat LTO pipeline). The plan is to make the switch after we update to LLVM 13.

Remove dead or useless code from Session

This is a more principled follow-up to https://github.com/rust-lang/rust/pull/83185#discussion_r601753839.

- Rename `Parser::span_fatal_err` -> `Parser::span_err`
- Remove some unnecessary uses of `struct_span_fatal`
- Make `Diagnostic::span_fatal` unconditionally raise an error
- Add `impl Deref<Target = Handler>` for Session and remove all functions that are exactly the same as their Handler counterparts
- Note why `Handler::fatal` is different from `Sesssion::fatal`
- Remove unused `opt_span_warn` function

r? `@oli-obk` or `@estebank`

Remove `FakeDefId::expect_local()`

This function returned a fake `DefIndex`, with no indication that it was
fake, when it was provided with a `FakeDefId::Fake`. Every use of the
function uses the returned `DefIndex` in a call to
`tcx.local_def_id_to_hir_id()`, which I'm pretty sure would panic if it
were given a fake `DefIndex`.

I removed the function and replaced all calls to it with a call to
`expect_real()` followed by `DefId::expect_local()` (that's a function
on the *real* `DefId`).

It had no callers which didn't immediately call `raise()`, and this
unifies the behavior with `Session`.

All of them immediately called `emit()` then `raise()`, so they could
just call `span_fatal` directly.

The name was misleading, it wasn't actually a fatal error.

Enable `-W semicolon_in_expressions_from_macros` in bootstrap

Now that stdarch has been updated, we can do this without breaking the
build.

Now, in the case that the function is not inlined, the panic location
will be the caller's location, which is more helpful since the panic is
not `expect_real()`'s fault.

This function returned a fake `DefIndex`, with no indication that it was
fake, when it was provided with a `FakeDefId::Fake`. Every use of the
function uses the returned `DefIndex` in a call to
`tcx.local_def_id_to_hir_id()`, which I'm pretty sure would panic if it
were given a fake `DefIndex`.

I removed the function and replaced all calls to it with a call to
`expect_real()` followed by `DefId::expect_local()` (that's a function
on the *real* `DefId`).

Now that stdarch has been updated, we can do this without breaking the
build.

Bump stdarch submodule

Major changes:
- More AVX-512 intrinsics.
- More ARM & AArch64 NEON intrinsics.
- Updated unstable WASM intrinsics to latest draft standards.
- Intrinsics that previously used `#[rustc_args_required_const]` now use const generics. See #83167 for more details.
- `std_detect` is now a separate crate instead of a submodule of `std`.

Update Miri

Fixes #85027

r? `@RalfJung`

rustdoc: Stop special casing `broken_intra_doc_links` unnecessarily

This updates the LLVM submodule with recent LLVM 12.x fixes. In
particular, it resolves an assertion failure when targeting
AArch64 at O0.

And report an error if parsing the additional pass pipeline fails.
Threading through the error accounts for most of the changes here.

This doesn't seem to be necessary anymore, although I don't know
at which point or why that changed.

Forcing -O1 makes some tests fail under NewPM, because NewPM also
performs inlining at -O1, so it ends up performing much more
optimization in practice than before.

This causes an assertion failure under NewPM, because it also ends
up disabling the NameAnonGlobals pass.

Instead pass -Copt-level=0 to disable optimizations. If that should
be insufficient, we can use -C no-prepopulate-passes.

Don't use "passes" for this purpose, explicitly insert it into
the correct place in the pipeline instead.

To allow it to have an LLVM version dependent default.

Update cargo

7 commits in f3e13226d6d17a2bc5f325303494b43a45f53b7f..e51522ab3db23b0d8f1de54eb1f0113924896331
2021-04-30 21:50:27 +0000 to 2021-05-07 21:29:52 +0000
- Add CARGO_TARGET_TMPDIR env var for integration tests & benches (rust-lang/cargo#9375)
- Bump to 0.55.0, update changelog (rust-lang/cargo#9464)
- Some updates to the unstable documentation (rust-lang/cargo#9457)
- Add CARGO_PROFILE_<name>_SPLIT_DEBUGINFO to env docs. (rust-lang/cargo#9456)
- Add `report` subcommand. (rust-lang/cargo#9438)
- Respect Cargo.toml `[package.exclude]` even not in a git repo. (rust-lang/cargo#9186)
- Document the other crates in the codebase in the contrib guide. (rust-lang/cargo#9439)

Update RLS

This mostly just includes https://github.com/rust-lang/rls/commit/e33f4e68496b296dedb100e297dc4451f169b2b3 so that this fixes #85055 (clippy-related breakage).