[clang] [Clang][Sema] Implement approved resolution for CWG2858 (PR #88042)

[Erich Keane via cfe-commits]

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

@endilll says 'Good to go' with the dr-status updated, so I'll approve.

https://github.com/llvm/llvm-project/pull/88042