[llvm] [X86] Added sincos vector lib codegen test coverage (PR #183702)

[Simon Pilgrim via llvm-commits]

RKSimon wrote:

@Aadarsh-Keshri - cheers - as a followup please could you still add the sincospi test file you have but just test on libmvec if that works and its just an amdlibm issue?

https://github.com/llvm/llvm-project/pull/183702