[clang] [clang/AST] Make it possible to use SwiftAttr in type context (PR #108631)

[Erich Keane via cfe-commits]

erichkeane wrote:

> > That being said, one question is whether we actually need type attributes to be propagated in this case for Swift's interop.
> 
> I don't think we do, we need swift_attr to help us augment Objective-C APIs to make existing frameworks play well with Swift concurrency. I think C++ Interoperability only uses them in limited set of cases which don't involve templates.

What about ObjC++?  We support that as well, and I'd like for us to not lose that ability too.

https://github.com/llvm/llvm-project/pull/108631