libhidlallocatorutils: IMemoryHeap -> hidl_memory

Several places  originally did this conversion itself.
However, it's gross for them to have to care about the hidl
detail that IAllocator ashmem corresponds to framework
IMemoryHeap. Instead, we hide that behind a hidl-provided
function which can modify the opaque data in lock-step
with the allocator hal.

Bug: 34234561
Test: boot and use with DRM
Change-Id: Ia6b9b70fe9573da1518f3ee870e8f3232a8738bb
4 files changed