[llvm] [InstCombine] Support gep nuw in icmp folds (PR #118472)

[David Benjamin via llvm-commits]

davidben wrote:

Relatedly, this seems a good reason to do https://github.com/llvm/llvm-project/issues/119040. Any code that has a pointer wraparound problem probably also has a problem with `ptr + n` escaping the bounds of `ptr`'s allocation, and that one is much more likely to be hit in testing.

https://github.com/llvm/llvm-project/pull/118472