[llvm] [InstSimplify] Add basic constant folding for `llvm.sincos` (PR #114527)

[Benjamin Maxwell via llvm-commits]

MacDue wrote:

Reverted this for now (https://github.com/llvm/llvm-project/pull/119149). I'll look into the buildbot issues and reland tomorrow. 

https://github.com/llvm/llvm-project/pull/114527