[clang] [clang][x86] Add constexpr support for VNNI intrinsics (PR #190549)

[Akash Deo via cfe-commits]

AkashDeoNU wrote:

> Sorry, I may have misread the mask/maskz tests - as long as we have test coverage for every intrinsic that's fine.
> 
> If you made the existing tests arguments more non-uniform you could actually reduce the number of tests (if you look you have a lot more TEST_CONSTEXPR tests than most intrinsics do) - since VNNI performs cross-element access its useful to find bugs if you avoid the elements being all the same.

Great! I will incorporate those changes tonight, then re-request reviews. Thanks for the feedback. 

https://github.com/llvm/llvm-project/pull/190549