Currently, the Rust pretty-printers are registered in gdb using the
uninformative name "lookup":

    (gdb) info pretty-printer
    global pretty-printers:
    [...]
    objfile /home/tromey/[...]
      lookup

It's nicer for users if the top-level registration is given a clear
name.  Additionally, gdb lets users individually enable and disable
specific printers, provided they are registered correctly.

This patch implements both these ideas.  Now the output looks like:

    (gdb) info pretty-printer
    global pretty-printers:
    [...]
    objfile /home/tromey/[...]
      rust
	StdArc
	StdBTreeMap
	StdBTreeSet
	StdCell
	StdHashMap
	StdHashSet
	StdNonZeroNumber
	StdOsString
	StdRc
	StdRef
	StdRefCell
	StdRefMut
	StdSlice
	StdStr
	StdString
	StdVec
	StdVecDeque

…pe, r=matthewjasper

Location-insensitive polonius: consider a loan escaping if an SCC has member constraints applied only

The location-insensitive analysis considered loans to escape if there were member constraints, which makes *some* sense for scopes and matches the scopes that NLL computes on all the tests.

However, polonius and NLLs differ on the fuzzed case rust-lang#116657, where an SCC has member constraints but no applied ones (and is kinda surprising). The existing UI tests with member constraints impacting scopes all have some constraint applied.

This PR changes the location-insensitive analysis to consider a loan to escape if there are applied member constraints, and for extra paranoia/insurance via fuzzing and crater: actually checks the constraint's min choice is indeed a universal region as we expect. (This could be turned into a `debug_assert` and early return as a slight optimization after these periods of verification)

The 4 UI tests where member constraints are meaningful for computing scopes still pass obviously, and this also fixes rust-lang#116657.

r? `@matthewjasper`

…rk-Simulacrum

Rewrite gdb pretty-printer registration

Currently, the Rust pretty-printers are registered in gdb using the uninformative name "lookup":

    (gdb) info pretty-printer
    global pretty-printers:
    [...]
    objfile /home/tromey/[...]
      lookup

It's nicer for users if the top-level registration is given a clear name.  Additionally, gdb lets users individually enable and disable specific printers, provided they are registered correctly.

This patch implements both these ideas.  Now the output looks like:

    (gdb) info pretty-printer
    global pretty-printers:
    [...]
    objfile /home/tromey/[...]
      rust
	StdArc
	StdBTreeMap
	StdBTreeSet
	StdCell
	StdHashMap
	StdHashSet
	StdNonZeroNumber
	StdOsString
	StdRc
	StdRef
	StdRefCell
	StdRefMut
	StdSlice
	StdStr
	StdString
	StdVec
	StdVecDeque

…=cjgillot

coverage: Add UI tests for values accepted by `-Cinstrument-coverage`

I wanted to clean up the code in `parse_instrument_coverage`, but it occurred to me that we currently don't have any UI tests for the various stable and unstable values supported by this flag.

---

Normally it might be overkill to individually test all the different variants of `on`/`off`, but in this case the parsing of those values is mixed in with some other custom code, so I think it's worthwhile being thorough.

Eliminate rustc_attrs::builtin::handle_errors in favor of emitting errors directly

Suggested in rust-lang#116773 (review).

This `handle_errors` function is originally from rust-lang#34531, in which it was useful because it allowed error messages and error codes (`E0542`) for multiple occurrences of the same error to be centralized in one place. For example rather than repeating this diagnostic in 2 places:

```rust
span_err!(diagnostic, attr.span, E0542, "missing 'since'");
```

one could repeat this instead:

```rust
handle_errors(diagnostic, attr.span, AttrError::MissingSince);
```

ensuring that all "missing 'since'" errors always remained consistent in message and error code.

Over time as error messages and error codes got factored to fluent diagnostics (rust-lang#100836), this rationale no longer applies. The new code has the same benefit while being less verbose (+73, -128).

```rust
sess.emit_err(session_diagnostics::MissingSince { span: attr.span });
```

r? `@cjgillot`

…ename-suggestion, r=lqd

Fix suggestion for renamed coroutines feature

This fixes a small typo from rust-lang#116958