MNEMONIC-60:Apply Transaction, Retrievable interfaces to class VolatileMemAllocator

[lcy0816]

The current implementation of class VolatileMemAllocator does not support retrieval operations so it is not possible to temporarily forget cached durable objects efficiently like class NonVolatileMemAllocator does, logically, volatile memory should be retrievable for durable object graphs in a applications/frameworks run-time session.
In addition, durable native computing must based on retrievable interface, therefore the VolatileMemAllocator should implement retrievable interface to support forgettable object graphs and durable native computing.