Auto merge of #126736 - matthiaskrgr:rollup-rb20oe3, r=matthiaskrgr

Rollup of 7 pull requests

Successful merges:

 - #126380 (Add std Xtensa targets support)
 - #126636 (Resolve Clippy `f16` and `f128` `unimplemented!`/`FIXME`s )
 - #126659 (More status-quo tests for the `#[coverage(..)]` attribute)
 - #126711 (Make Option::as_[mut_]slice const)
 - #126717 (Clean up some comments near `use` declarations)
 - #126719 (Fix assertion failure for some `Expect` diagnostics.)
 - #126730 (Add opaque type corner case test)

r? `@ghost`
`@rustbot` modify labels: rollup

Author: bors