[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)

[Ilya Biryukov via cfe-commits]

ilya-biryukov wrote:

Heh, of course! Now that you say it, that's quite obvious.

Do you think is fix is just around the corner or will it take a long time?
This blocks our internal compiler release and there is no workaround we could easily employ.

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