[clang] [Clang] Add __scoped_atomic_uinc_wrap and __scoped_atomic_udec_wrap builtins (PR #168666)

[Joseph Huber via cfe-commits]

jhuber6 wrote:

I was going to expand my scoped atomic to handle this but found someone already did it, nice. But, I wonder if we should've made an `__atomic_` version to accompany this. Also the naming convention doesn't seem right here, I would've expected `__atomic_fetch_uinc` or similar.

https://github.com/llvm/llvm-project/pull/168666