[clang] [clang] Warn on mismatched RequiresCapability attributes (PR #67520)

[Timm Baeder via cfe-commits]

tbaederr wrote:

> Also, this should be extended to almost all other thread safety attributes. For a start, do one or two so that we can see what it looks like.

This ends up being pretty ugly since we're collecting the arguments right now, but most of the other attributes don't have arguments or have no `::args()`.

https://github.com/llvm/llvm-project/pull/67520