Auto merge of #120628 - workingjubilee:reimpl-meaningful-test-name-lint, r=compiler-errors

Reimpl meaningful test name lint MCP658

This reintroduces the tidy rule originally proposed in https://github.com/rust-lang/rust/pull/113583 that then became an MCP in https://github.com/rust-lang/compiler-team/issues/658 which eventually surfaced a quite-reasonable request for a diagnostic enhancement. I have added that to the rule. It produces output like this:
```
tidy error: file `ui/unsized/issue-115809.rs` must begin with a descriptive name, try `{reason}-issue-115809.rs`
tidy error: file `ui/unsized/issue-115203.rs` must begin with a descriptive name, try `{reason}-issue-115203.rs`
tidy error: file `ui/privacy/issue-113860-2.rs` must begin with a descriptive name, try `{reason}-issue-113860.rs`
tidy error: file `ui/privacy/issue-117997.rs` must begin with a descriptive name, try `{reason}-issue-117997.rs`
tidy error: file `ui/privacy/issue-119463.rs` must begin with a descriptive name, try `{reason}-issue-119463.rs`
tidy error: file `ui/privacy/auxiliary/issue-117997.rs` must begin with a descriptive name, try `{reason}-issue-117997.rs`
tidy error: file `ui/privacy/auxiliary/issue-119463-extern.rs` must begin with a descriptive name, try `{reason}-issue-119463.rs`
tidy error: file `ui/privacy/issue-113860-1.rs` must begin with a descriptive name, try `{reason}-issue-113860.rs`
tidy error: file `ui/privacy/issue-113860.rs` must begin with a descriptive name, try `{reason}-issue-113860.rs`
tidy error: file `ui/const-generics/generic_const_exprs/const_kind_expr/issue_114151.rs` must begin with a descriptive name, try `{reason}-issue-114151.rs`
tidy error: file `ui/did_you_mean/issue-114112.rs` must begin with a descriptive name, try `{reason}-issue-114112.rs`
tidy error: file `ui/did_you_mean/issue-105225.rs` must begin with a descriptive name, try `{reason}-issue-105225.rs`
tidy error: file `ui/did_you_mean/issue-105225-named-args.rs` must begin with a descriptive name, try `{reason}-issue-105225.rs`
```

You get the idea.

There are some tests which merely would require reordering of the name according to the rule. I could modify the diagnostic further to identify those, but doing such would make it prone to bad suggestions. I have opted to trust contributors to recognize the diagnostic is robotic, as the pattern we are linting on is easier to match if we do not speculate on what parts of the name are meaningful: sometimes a word is a reason, but sometimes it is a mere "tag", such as with a pair like:
- issue-314159265-blue.rs
- issue-314159265-red.rs

Starting them with `red-` and `blue-` means they do not sort together, despite being related, and the color names are still not very descriptive. Recognizing a good name is an open-ended task, though this pair might be:
- colored-circle-gen-blue.rs
- colored-circle-gen-red.rs

Deciding exactly *how* to solve this is not the business of tidy, only recognizing a what.

r? `@compiler-errors`

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