[clang] [Clang] Bypass TAD during overload resolution if a perfect match exists (PR #136018)

[Erich Keane via cfe-commits]

https://github.com/erichkeane commented:

Discussed elsewhere, but in a touch of "lets leave it better than we found it", can we make an `assert(HasFinalConversion)` everywhere else we access `FinalConversion`? 

https://github.com/llvm/llvm-project/pull/136018