… (RFC 2383)

…ature, r=Amanieu

Stabilise `aarch64_target_feature`

This PR stabilises `aarch64_target_feature` - see rust-lang#90620

…ata, r=wesleywiser

Type params and assoc types have unit metadata if they are sized

Extend the logic in `Pointee` projection to ensure that we can satisfy `<T as Pointee>::Metadata = ()` if `T: Sized`.

cc: `@SimonSapin` and rust-lang#93959

…-party, r=flip1995,wesleywiser

Improve `expect` impl and handle `#[expect(unfulfilled_lint_expectations)]` (RFC 2383)

This PR updates unstable `ExpectationIds` in stashed diagnostics and adds some asserts to ensure that the stored expectations are really empty in the end. Additionally, it handles the `#[expect(unfulfilled_lint_expectations)]` case.

According to the [Errors and lints docs](https://rustc-dev-guide.rust-lang.org/diagnostics.html#diagnostic-levels) the `error` level should only be used _"when the compiler detects a problem that makes it unable to compile the program"_. As this isn't the case with `#[expect(unfulfilled_lint_expectations)]` I decided to only create a warning. To avoid adding a new lint only for this case, I simply emit a `unfulfilled_lint_expectations` diagnostic with an additional note.

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r? `@wesleywiser` I'm requesting a review from you since you reviewed the previous PR rust-lang#87835. You are welcome to reassign it if you're busy 🙃

rfc: [RFC-2383](https://rust-lang.github.io/rfcs/2383-lint-reasons.html)

tracking issue: rust-lang#85549

cc: `@flip1995` In case you're also interested in this :)

Fix remaining meta-variable expression TODOs

As promised on rust-lang#93545.

cc rust-lang#83527
cc `@mark-i-m`
cc `@petrochenkov`

update miri

Fixes rust-lang#94910
r? `@ghost`