[clang] [llvm] [IR] Add getelementptr nusw and nuw flags (PR #90824)

[Antonio Frighetto via cfe-commits]

antoniofrighetto wrote:

Are the TODOs encompassing all the cases? Why we don't want to set the flags in `PHITransAddr` as well?

https://github.com/llvm/llvm-project/pull/90824