libstdc++: Fix std::ranges::iota is not included in numeric [PR108760]

Before this patch, using std::ranges::iota required including
<algorithm> when it should have been sufficient to only include
<numeric>.

libstdc++-v3/ChangeLog:

	PR libstdc++/108760
	* include/bits/ranges_algo.h (ranges::out_value_result):
	Move to <bits/ranges_algobase.h>.
	(ranges::iota_result, ranges::__iota_fn, ranges::iota): Move to
	<numeric>.
	* include/bits/ranges_algobase.h (ranges::out_value_result):
	Move to here.
	* include/std/numeric (ranges::iota_result, ranges::__iota_fn)
	(ranges::iota): Move to here.
	* testsuite/25_algorithms/iota/1.cc: Renamed to ...
	* testsuite/26_numerics/iota/2.cc: ... here.

Signed-off-by: Michael Levine <mlevine55@bloomberg.net>