Implement P2494R2 Relaxing range adaptors to allow for move only types
According to the words in P2494R2, I haven't add new test for drop_while_view, take_while_view and filter_view, because these views has the requirement that the predicate is an indirect_unary_predicate, which requires that the predicate is copy_constructible, so they still can't accept move only types as predicate.
[P2483R0] also suggests future work to relax the requirements on the predicate types stored by standard views. This paper does not perform this relaxation, as the copy constructibility requirement is enshrined in the indirect callable concepts ([indirectcallable.indirectinvocable]). Thus, while this paper modifies the views that currently use copyable-box for user provided predicates, it only does so to apply the rename of the exposition-only type to movable-box; it does not change any of the constraints on those views. It does, however, relax the requirements on invocables accepted by the transform family of views, because those are not constrained using the indirect callable concepts.