This implements the wording changes of P2328R0 "join_view should join
all views of ranges".
libstdc++-v3/ChangeLog:
* include/std/ranges (__detail::__non_propating_cache): Define
as per P2328.
(join_view): Remove constraints on the value and reference types
of the wrapped iterator type as per P2328.
(join_view::_Iterator::_M_satisfy): Adjust as per P2328.
(join_view::_Iterator::operator++): Likewise.
(join_view::_M_inner): Use __non_propating_cache as per P2328.
Remove now-redundant use of __maybe_present_t.
* testsuite/std/ranges/adaptors/join.cc: Include <array>.
(test10): New test.
237dde3d03