Update std::allocator interface

[m4drat]

We already have default std::allocator interface that uses Allocate/Deallocate functions directly. But we are going to get rid of these functions in the future (due to some problems described in #30). So we have to refactor this interface in such a way, so it's possible to use it without presence of Allocate/Deallocate methods.

[m4drat]

Currently I don't think that it is possible to implement such an interface.
SA: https://stackoverflow.com/questions/65645904/implementing-a-custom-allocator-with-fancy-pointers