[llvm] [Attr] Add `noipa` function attribute (PR #203304)

[J. Ryan Stinnett via llvm-commits]

jryans wrote:

For each of the passes @nikic highlighted [above](https://github.com/llvm/llvm-project/pull/203304#issuecomment-4682379357), I have adjusted the pass logic to check whether IPA is allowed for the current function, which resolves all of these AI-discovered issues. I have added each of the provided tests as well, and I verified that they only worked after fixing the relevant pass logic. I also added a test to ensure `noipa` is distinct from `noinline`.

I also manually reviewed the logic of all other IPO transforms to see if any other passes should be modified. I also searched for related helpers (like `hasLocalLinkage` etc.) to try to spot other areas to modify. I did not notice any additional passes to update from this manual search.

https://github.com/llvm/llvm-project/pull/203304