[clang] [Clang] Implement P2809: Trivial infinite loops are not Undefined Behavior (PR #90066)

[Erich Keane via cfe-commits]

https://github.com/erichkeane approved this pull request.

This LGTM, but please give @efriedma-quic a day or two to confirm this looks right for him too.

https://github.com/llvm/llvm-project/pull/90066