[llvm] [LICM] Rewrite noConflictingReadWrites to walk MemorySSA graph (PR #191468)

[via llvm-commits]

https://github.com/CarolineConcatto commented:

I know that Nikita said this should be looked once [PR#187529](https://github.com/llvm/llvm-project/pull/187529)  was addressed to remove redundant check with memory use.
But as this patch is similar to the one I also have upstream, maybe it is worth to leave some comments.

https://github.com/llvm/llvm-project/pull/191468