Rollup merge of #124928 - okaneco:trim_ascii, r=workingjubilee

Stabilize `byte_slice_trim_ascii` for `&[u8]`/`&str`

Remove feature from documentation examples
Update intra-doc link for `u8::is_ascii_whitespace` on `&[u8]` functions

Closes #94035

FCP has successfully completed rust-lang/rust#94035 (comment)