Camera: Add PreviewFrameScheduler to address preview jitter

The ideal viewfinder user experience is that frames are presented to the
user in the same cadence as outputed by the camera sensor. However, the
processing latency between frames could vary, due to factors such
as CPU load, difference in request settings, etc. This frame processing
latency results in variation in presentation of frames to the user.

Improve the user experience by:

1. Cache preview buffers in PreviewFrameScheduler.
2. For each choreographer callback, queue the oldest preview buffer,
   with the best matching presentation timestamp. Frame N's
   presentation timestamp is the choreographer timeline timestamp closest to
   (Frame N-1's presentation time + capture interval between frame N-1 and N).
3. Maintain at most 2 queue-able buffers. If a 3rd preview buffer becomes
   available, queue it to the buffer queue right away.

Test: Run GoogleCamera video mode and observe smoother viewfinder
Test: Observe surfaceflinger trace when running viewfinder
Test: Camera CTS
Bug: 200306379
Change-Id: I791c841aaded2acd112de8f7e99a131443b21e11