[libc++][memory] Implement specializations for P1132R8: `out_ptr` - a scalable output pointer abstraction

[Zingam]

#73618 implemented P1132R8: out_ptr - a scalable output pointer abstraction as close as possible to the wording in the Standard. During the review of #73618 it was requested to provide specializations of std::out_ptr.

This issue is to track the implementation of any improvements that can be provided by implementing specializations (std::shared_ptr, std::unique_ptr) of std::out_ptr_t and std::inout_ptr_t.