libstdc++: Implement remaining piece of LWG 3448

libstdc++: Implement remaining piece of LWG 3448

Almost all of the proposed resolution for LWG 3448 is already
implemented; the only part left is to adjust the return type of
transform_view::sentinel::operator-.

libstdc++-v3/ChangeLog:

	PR libstdc++/95322
	* include/std/ranges (transform_view::sentinel::__distance_from):
	Give this a deduced return type.
	(transform_view::sentinel::operator-): Adjust the return type so
	that it's based on the constness of the iterator rather than
	that of the sentinel.
	* testsuite/std/ranges/adaptors/95322.cc: Refer to LWG 3488.