[clang] [OpenACC] Implement Sema work for OpenACC Clauses (PR #87821)

[Vlad Serebrennikov via cfe-commits]

https://github.com/Endilll commented:

I hope #87634 will be merged soon, so you can get rid of `SemaRef.Diag()` here.

https://github.com/llvm/llvm-project/pull/87821