Add IMemoryToken and the HidlMemoryToken

The IMemoryToken is an interface which composes shared memory.
It provides a get() method, which returns an instance of hidl_memory
that always refer to the same memory.

The HidlMemoryToken is an implementation of the IMemoryToken.

Bug: 69640337
Test: hidl_test
Change-Id: Ida32a7971ba31e99f724c18159cf2e1f699b73b8
6 files changed