[clang] [llvm] [Sanitizers] Support sanitizer instrumentation regions in KMSAN, KASAN, KCOV and KCSAN (PR #231374)

[Alexander Potapenko via cfe-commits]

ramosian-glider wrote:

@melver @vitalybuka this is a lot of code. If you prefer, I can split off the first two patches (adding the intrinsics + KMSAN support) and send the rest separately.

https://github.com/llvm/llvm-project/pull/231374