[clang] [clang] Add support for `__ptrauth` being applied to integer types (PR #137580)

[Oliver Hunt via cfe-commits]

ojhunt wrote:

> Would it make sense to add the feature macro to your downstream instead? e.g., downstream supports `__has_feature(ptrauth_restricted_intptr)` and upstream would return `false` for it.

We have that, I just need to determine if there's any code that treats the lack of that qualifier as meaning no ptrauth+intptr - the current PR does not technically allow this to be distinguished, which may be ok, it just requires me doing some work first - given the lack of a unique qualifier the current PR intentionally doesn't have a feature/extension flag.

I think it would be reasonable to consider it done at this point, and if we do run into backwards compatibility problems we can discuss it again at that point, does that seem reasonable?

As it is, with the removal of the distinct qualifier this PR becomes much simpler - just changes the exact type query, and updates integer codegen in the places it matters.

https://github.com/llvm/llvm-project/pull/137580