Auto merge of rust-lang#148014 - jhpratt:rollup-aglren3, r=jhpratt

Rollup of 3 pull requests

Successful merges:

 - rust-lang#134316 (Add `String::replace_first` and `String::replace_last`)
 - rust-lang#147713 (Retire ast::TyAliasWhereClauses.)
 - rust-lang#148011 (Revert constification of `AsRef for Cow` due to inference failure )

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

Author: bors