libstdc++: Simplify constraints for std::any construction [PR104242]

libstdc++: Simplify constraints for std::any construction [PR104242]

Partially revert r12-4190-g6da36b7d0e43b6f9281c65c19a025d4888a25b2d
because using __and_<..., is_copy_constructible<T>> when T is incomplete
results in an error about deriving from is_copy_constructible<T> when
that is incomplete. I don't know how to fix that, so this simply
restores the previous constraint which worked in this case (even though
I think it's technically undefined to use is_copy_constructible<T> with
incomplete T). This doesn't restore exactly what we had before, but uses
the is_copy_constructible_v and __is_in_place_type_v variable templates
instead of the ::value member.

libstdc++-v3/ChangeLog:

	PR libstdc++/104242
	* include/std/any (any(T&&)): Revert change to constraints.
	* testsuite/20_util/any/cons/104242.cc: New test.