[clang] [clang-tools-extra] [llvm] [clang] Introduce diagnostics suppression mappings (PR #112517)

[kadir çetinkaya via cfe-commits]

kadircet wrote:

thanks for the review!

@AaronBallman i'd like to land this early next week and start testing/polishing. It'd be great if you can give some explicit LGTM.

https://github.com/llvm/llvm-project/pull/112517