[clang] Add clang atomic control options and attribute (PR #114841)

[Yaxun Liu via cfe-commits]

yxsamliu wrote:

> Mostly drive-by comments. Don't have strong opinion on either the attributes themselves nor how the values get parsed.
> 
> One thing that's missing is the documentation for the attributes. Their format and meaning are far from obvious and should be documented along with other clang-specific attributes.

will add documentation for atomic attributes

https://github.com/llvm/llvm-project/pull/114841