[clang] [clang] Rename ReadPCHAndPreprocessAction (NFC) (PR #122390)

[Jan Svoboda via cfe-commits]

jansvoboda11 wrote:

I agree that the name can be confusing. I think the original motivation for this name was to avoid spreading the concept of modular dependency scanning through the Clang codebase. Could we move this class into `Tooling/DependencyScanning` to keep that concept self-contained and outside the base Clang libraries?

https://github.com/llvm/llvm-project/pull/122390