Auto merge of #136534 - jhpratt:rollup-dnz57dq, r=jhpratt

Rollup of 6 pull requests

Successful merges:

 - #136398 (add UnsafeCell direct access APIs)
 - #136465 (Some `rustc_middle` cleanups)
 - #136479 (std::fs: further simplify dirent64 handling)
 - #136504 (Fix last compare-mode false negatives in tests)
 - #136511 (Add `cast_signed` and `cast_unsigned` methods for `NonZero` types)
 - #136518 (Add note about `FnPtr` trait being exposed as public bound)

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