[vr] Add DVR API to get native handle for buffers

This is required to support GPU late latching features in
VRCore. This can be removed once vendors support using
AHardwareBuffer instead of int fd for shared memory
buffer objects.

Bug: b/37472908
Test: builds and runs
Change-Id: I2a957723c4025773181071491a45a53b83e5ba64
4 files changed