Fixes rust-lang#68542

Co-Authored-By: Dylan DPC <dylan.dpc@gmail.com>

…ue, r=alexcrichton

Stabilize the debug_map_key_value feature

RFC: rust-lang/rfcs#2696
Tracking issue: rust-lang#62482

Stabilizes the `debug_map_key_value` feature, which covers:

```rust
impl<'a, 'b> DebugMap<'a, 'b> {
    pub fn key(&mut self, key: &dyn fmt::Debug) -> &mut DebugMap<'a, 'b> {}
    pub fn value(&mut self, value: &dyn fmt::Debug) -> &mut DebugMap<'a, 'b> {}
}
```

These methods are small and self-contained, and are used as the basis for the existing `DebugMap::entry` method, so have been used in the wild for the last 6 months or so.

…lan-DPC

Clean up E0205 explanation

r? @Dylan-DPC

…lan-DPC

Clean up E0207 explanation

r? @Dylan-DPC

…lan-DPC

clean up E0214 explanation

r? @Dylan-DPC

…r=Dylan-DPC

clean up error codes explanation

r? @Dylan-DPC

Don't call `tcx.fn_sig` on closures

Fixes rust-lang#68542

…chton

Bump LLVM submodule to fix LLVM assertion failure in MSP430 interrupt generation.

This PR brings in changes introduced by [this cherry-pick](rust-lang/llvm-project#37) to the Rust repository.

Nightlies downloaded from `rustup` do not appear to have llvm assertions enabled; the assertion failure [sometimes](YuhanLiin/msp430fr2355-quickstart#3) causes link errors that shouldn't occur. I couldn't find any indication of other bugs; however, it should still be fixed.

check_match: extract common logic

This is part of work on `hir::ExprKind::Let` which I thought made sense on its own (though makes even more sense with `::Let`).

r? @oli-obk

…lan-DPC

Clean up E0262 explanation

r? @Dylan-DPC

Disable the testcase for Vxworks.

r? @alexcrichton

…nup-crew, r=Dylan-DPC

Add support for icebreakers-cleanup-crew commands

r? @nikomatsakis