Camera2: Add MOTION_TRACKING capability/intent, and lens poseReference

- MOTION_TRACKING capability defines a camera with accurate lens calibration
  values, accurate timestamps relative to the inertial sensors, and ability
  to limit exposure time to 20ms max.
- Add android.lens.poseReference for supporting gyroscope-centered lens calibration
  data for MOTION_TRACKING.
- Minor changes to some docs formatting.

Test: Builds
Bug: 63629224
Change-Id: Ic303240890c709725f60e69dfff76beea4a0ef91