libstdc++: Implement ranges::join_with_view from P2441R2

libstdc++: Implement ranges::join_with_view from P2441R2

libstdc++-v3/ChangeLog:

	* include/std/ranges: Include <variant> for C++23.
	(__detail::__compatible_joinable_ranges): Define.
	(__detail::__bidirectional_common): Define.
	(join_with_view): Define.
	(join_with_view::_Iterator): Define.
	(join_with_view::_Sentinel): Define.
	(views::__detail::__can_join_with_view): Define.
	(views::_JoinWith, views::join_with): Define.
	* testsuite/std/ranges/adaptors/join_with/1.cc: New test.