[clang] [clang][modules] Erase PCMs not meeting expectations from in-memory cache (PR #177004)

[Volodymyr Sapsai via cfe-commits]

https://github.com/vsapsai commented:

I think my main concern with this approach is that to use `ModuleManager` properly you need to know more of its implementation, when and how it uses `InMemoryModuleCache` and how to "fix" this usage.

https://github.com/llvm/llvm-project/pull/177004