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

[Erich Keane via cfe-commits]

erichkeane wrote:

Build failure is completely unrelated, but I think this does everything you've asked for @alexey-bataev .  Let me know what you think!

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