Make `is_sorted[_by_key]` require `Ord` instead of `PartialOrd` and remove `Iterator::is_sorted_by_key`#81382

LukasKalbertodt wants to merge 3 commits intorust-lang:masterrust-lang/rust:masterfrom

LukasKalbertodt:make-is-sorted-require-ordLukasKalbertodt/rust:make-is-sorted-require-ordCopy head branch name to clipboard