[llvm] [LLVM][rtsan] Add RealtimeSanitizer transform pass (PR #101232)

[Chris Apple via llvm-commits]

cjappl wrote:

CC Reviewers @vitalybuka @MaskRay 

This review should be green once https://github.com/llvm/llvm-project/pull/100596 is merged, as this depends on the attribute existing

CC co-author @davidtrevelyan 

https://github.com/llvm/llvm-project/pull/101232