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

[kadir çetinkaya via cfe-commits]

https://github.com/kadircet commented:

> Note that there are a few open comments from previous iterations.

I tried to go over them, but github UI was ... suboptimal. So PLMK if you got some that aren't addressed in this revision as well.

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