Move-assign a random-access handle from another.
basic_random_access_handle & operator=( basic_random_access_handle && other);
This assignment operator moves a random-access handle from one object to another.
The other random-access handle object from which the move will occur.
Following the move, the moved-from object is in the same state as if constructed
using the basic_random_access_handle(const executor_type&)
constructor.