Auto merge of #88618 - m-ou-se:rollup-6tss5z6, r=m-ou-se

Rollup of 7 pull requests

Successful merges:

 - #88202 (Add an example for deriving PartialOrd on enums)
 - #88483 (Fix LLVM libunwind build for non-musl targets)
 - #88507 (Add test case for using `slice::fill` with MaybeUninit)
 - #88557 (small const generics cleanup)
 - #88579 (remove redundant / misplaced sentence from docs)
 - #88610 (Update outdated docs of array::IntoIter::new.)
 - #88613 (Update primitive docs for rust 2021.)

Failed merges:

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