libstdc++: Directly implement ranges::heap algos [PR100795]

libstdc++: Directly implement ranges::heap algos [PR100795]

ranges::push_heap, ranges::pop_heap, ranges::make_heap and
ranges::sort_heap are currently defined in terms of the corresponding
STL-style algorithms, but this is incorrect because the STL-style
algorithms rely on the legacy iterator system, and so misbehave when
passed a narrowly C++20 random access iterator.  The other ranges heap
algos, ranges::is_heap and ranges::is_heap_until, are implemented
directly already and have no known issues.

This patch reimplements these ranges:: algos directly instead, based
closely on the legacy stl_heap.h implementation, with the following
changes for compatibility with the C++20 iterator system:

  - handle non-common ranges by computing the corresponding end iterator
  - use ranges::iter_move instead of std::move(*iter)
  - use iter_value_t / iter_difference_t instead of iterator_traits

Besides these changes, the implementation of these algorithms is
intended to mirror the stl_heap.h implementations, for ease of
maintenance and review.

Note that we don't explicitly pass the projection function throughout,
instead we just create and pass a composite predicate via __make_comp_proj.

	PR libstdc++/100795

libstdc++-v3/ChangeLog:

	* include/bits/ranges_algo.h (__detail::__push_heap): New,
	based on the stl_heap.h implementation.
	(__push_heap_fn::operator()): Reimplement in terms of the above.
	(__detail::__adjust_heap): New, based on the stl_heap.h
	implementation.
	(__deatil::__pop_heap): Likewise.
	(__pop_heap_fn::operator()): Reimplement in terms of the above.
	(__make_heap_fn::operator()): Likewise.
	(__sort_heap_fn::operator()): Likewise.
	* testsuite/25_algorithms/heap/constrained.cc (test03): New
	test.

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