libdmabufheap: Introduce AllocSystem() API am: f7b3d5df5d

Original change: https://android-review.googlesource.com/c/platform/system/memory/libdmabufheap/+/1649887

Change-Id: I743c2c05e509be9b04d9b2a3d0ff90629350e11f
tree: ec0f0471d720e7d8a961cf4b4090c0ece8fdd84f
  1. include/
  2. tests/
  3. Android.bp
  4. BufferAllocator.cpp
  5. BufferAllocatorWrapper.cpp