libstdc++: Directly implement ranges::stable_sort [PR100795]

libstdc++: Directly implement ranges::stable_sort [PR100795]

	PR libstdc++/100795

libstdc++-v3/ChangeLog:

	* include/bits/ranges_algo.h (__detail::__move_merge): New,
	based on the stl_algo.h implementation.
	(__detail::__merge_sort_loop): Likewise.
	(__detail::__chunk_insertion_sort): Likewise.
	(__detail::__merge_sort_with_buffer): Likewise.
	(__detail::__stable_sort_adaptive): Likewise.
	(__detail::__stable_sort_adaptive_resize): Likewise.
	(__detail::__inplace_stable_sort): Likewise.
	(__stable_sort_fn::operator()): Reimplement in terms of the above.
	* testsuite/25_algorithms/stable_sort/constrained.cc:

Reviewed-by: Jonathan Wakely <jwakely@redhat.com>