Refactor VrFlinger to use BufferHubQueue

1/ Remove DisplayRPC::AllocateBuffer, as individual buffer allocation
is now handled by BufferHubQueue.
2/ Reimplement native_buffer_queue using bufferhubqueue.
3/ Hook up consumer queue in DisplaySurface.
4/ Remove epoll_event_dispatcher as its no longer being used.

Bug: 36033302
Test: Built and ran particles.apk
Change-Id: I38ee1c57195888ede935ebc50119bcb7e4ab4e36