libdmabufheap: Introduce AllocSystem() API am: 4c75b4a168

Original change: https://googleplex-android-review.googlesource.com/c/platform/system/memory/libdmabufheap/+/13974538

Change-Id: I8dbd904d6c94259f65026c18db1e502f08c0eef4
tree: ec0f0471d720e7d8a961cf4b4090c0ece8fdd84f
  1. include/
  2. tests/
  3. Android.bp
  4. BufferAllocator.cpp
  5. BufferAllocatorWrapper.cpp