[clang] [clang-tools-extra] Reapply "[Clang][Sema] Diagnose class member access expressions naming non-existent members of the current instantiation prior to instantiation in the absence of dependent base classes (#84050)" (PR #90152)

[Erich Keane via cfe-commits]

https://github.com/erichkeane commented:

Code changes LGTM, please add the tests, and I'll do another run at this.

https://github.com/llvm/llvm-project/pull/90152