[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)

[Vlad Serebrennikov via cfe-commits]

https://github.com/Endilll commented:

Changes to `Sema.h` and DR tests look good to me.

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