libstdc++: Relax range adaptors for move-only types (P2494R2)

libstdc++: Relax range adaptors for move-only types (P2494R2)

This is a C++23 feature that relaxes the constraints on some range
adaptors, to support move-only types.

libstdc++-v3/ChangeLog:

	* include/bits/version.def (ranges): Update value.
	* include/bits/version.h: Regenerate.
	* include/std/ranges (__detail::__boxable): Use
	move_constructible instead of copy_constructible for C++23.
	(__detail::__box<T>): Adjust constraints for partial
	specialization.
	(single_view, transform_view): Use __box_constructible instead
	of copy_constructible in constraints.
	(zip_transform_view, adjacent_transform_view, repeat_view): Use
	move_constructible instead of copy_constructible in constraints.
	* testsuite/std/ranges/adaptors/adjacent_transform/1.cc: Check
	construction from move-only argument.
	* testsuite/std/ranges/adaptors/transform.cc: Likewise.
	* testsuite/std/ranges/repeat/1.cc: Likewise.
	* testsuite/std/ranges/single_view.cc: Likewise.
	* testsuite/std/ranges/zip_transform/1.cc: Likewise.
	* testsuite/std/ranges/version_c++23.cc: Adjust expected value
	of __cpp_lib_ranges.