[clang] Match against all plugins when parsing microsoft attributes (PR #86426)

[Aaron Ballman via cfe-commits]

https://github.com/AaronBallman approved this pull request.

I'm really sorry for not realizing this was held up on me -- mea culpa!

This LGTM with a caveat: Clang has ignored Microsoft style attributes for a *long* time, so it's entirely possible that we don't correctly implement their parsing in all cases.

https://github.com/llvm/llvm-project/pull/86426