[clang] [clang][rtsan] Introduce realtime sanitizer codegen and driver (PR #102622)

[Chris Apple via cfe-commits]

cjappl wrote:

Tests continue to fail after reverting this: https://lab.llvm.org/buildbot/#/builders/159/builds/4474

I am trying to bisect locally, I will likely reland this with no modifications tomorrow if it continues to look like this did not contribute to the build failures. 

https://github.com/llvm/llvm-project/pull/102622