Rollup of 15 pull requests

Successful merges:

 - #144195 (Parser: Recover from attributes applied to types and generic args)
 - #144794 (Port `#[coroutine]` to the new attribute system)
 - #144835 (Anonymize binders in tail call sig)
 - #144861 (Stabilize `panic_payload_as_str` feature)
 - #144917 (Enforce tail call type is related to body return type in borrowck)
 - #144948 (we only merge candidates for trait and normalizes-to goals)
 - #144956 (Gate const trait syntax)
 - #144970 (rustdoc: fix caching of intra-doc links on reexports)
 - #144972 (add code example showing that file_prefix treats dotfiles as the name of a file, not an extension)
 - #144975 (`File::set_times`: Update documentation and example to support setting timestamps on directories)
 - #144977 (Fortify generic param default checks)
 - #144996 (simplifycfg: Mark as changed when start is modified in collapse goto chain)
 - #144998 (mir: Do not modify NonUse in `super_projection_elem`)
 - #145000 (Remove unneeded `stage` parameter when setting up stdlib Cargo)
 - #145008 (Fix rustdoc scrape examples crash)

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

Rollup merge of #144948 - lcnr:change-candidate-handling, r=compiler-errors

we only merge candidates for trait and normalizes-to goals

so change `fn try_merge_responses` to `fn try_merge_candidates` and just use candidates everywhere.

Potentially slightly faster than the alternative :3

r? ``@compiler-errors`` ``@BoxyUwU``