[clang] [Clang] Qualified functions can't decay into pointers (PR #90353)

[Vlad Serebrennikov via cfe-commits]

https://github.com/Endilll commented:

Current CWG713 behavior was introduced sometime after Clang 18, and is not affected by this patch.
Current CWG1584 behavior was introduced in Clang 7, and is also not affected by this patch. (https://godbolt.org/z/xYec9rP5x)
This PR is large enough already. I suggest to move those tests out to a separate PR.


https://github.com/llvm/llvm-project/pull/90353