[llvm] [IR] Add `llvm.sincos` intrinsic (PR #109825)

[Benjamin Maxwell via llvm-commits]

MacDue wrote:

> ```diff
> R = PromoteFloatRes_FSINCOS(N);
> ```

Not sure why, but my clang format (`18.1.8`) disagrees here (so I had to manually fix this).

https://github.com/llvm/llvm-project/pull/109825