Fix parameter types in copy_move_algo.hpp: iterator_traits::difference_type -> allocator_traits::size_type

[togermer]

Many of the functions inside copy_move_algo.hpp construct n objects using a specified Allocator, so the number of objects should be given as allocator_traits::size_type. The callers of these functions already use size_type, which currently leads to type conflicts if the InputIterator's difference_type is incompatible (e.g., smaller).

There is one exception in vector.hpp, where uninitialized_move_alloc_n() is called with a raw pointer difference. I static_casted this to size_type for compatibility.

There are several remaining functions inside copy_move_algo.hpp that use a difference_type parameter, but are independent of an allocator. I changed these to be agnostic of the integral type, as was already done with destroy_alloc_n(). (In fact, all of these functions eventually get called with allocator_traits::size_type arguments.)

[igaztanaga]

Thanks for the pull!