libstdc++: Implement LWG 3715 changes to view_interface::empty

libstdc++-v3/ChangeLog:

	* include/bits/ranges_util.h (view_interface::empty): Add
	preferred overloads that use ranges::size when the range is
	sized as per LWG 3715.
	* testsuite/std/ranges/adaptors/lwg3715.cc: New test.