[clang] Support `__is_trivially_copyable(int()&)==false` (#81298)

IMHO it would be productive to make a similar change for `typeid`, in
`ParseCXXTypeid`, in order to improve Clang's error message for
https://godbolt.org/z/oKKWxeYra
But that might be better done by adding a new DeclaratorContext
specifically for TypeidArg, instead of pretending that the argument to
`typeid` is a template argument, because I don't know what else that
change might affect.

Fixes #77585