Camera: Add extensions to CameraClient

This change includes the following gerrits:

  # This is a combination of 4 commits.
  # The first commit's message is:
  Camera: Enable Histogram feature.
  Link the histogram enable/disable commands from
  application to the HAL layer.
  Change-Id: I510c4e1798285ed1315bfb0d234fa76090659ba2

  # This is the 2nd commit message:
  Camera: Add support for ZSL burst mode.
  Added ability to set number of snapshots in burst mode.
  Change-Id: Ie0e7c8c0117b7adc985cfc92df79747ee6a5ea51

  # This is the 3rd commit message:
  CameraService: Adds support for longshot mode
  - This change introduces additional functionality inside
    CameraClient for supporting continuous compressed data
    callbacks. This is needed for 'Burst/Long shot' mode
    where we could have indefinite number of callbacks after
    capture is triggered.
  (cherrypicked from commit e4f502aa7cbe8875e8a1589024cdcf227c228a2b)
  Change-Id: Ia18ca9bdda7736c679db557e510870115089537a

  # This is the 4th commit message:
  CameraClient: Enables meta data notifications.
  Adds the needed functionality for enabling/disabling
  metadata messages depending on the camera client
  commands.
  Change-Id: I39d632b4742e83df5db5f86b12742aefc2480dfc
  Cherrypicked from 25bd97f5ec30e7942c3b1fdc96115da6028736f0

Change-Id: Ie930d20c962593e40a0767f9cf7d4385df8e2561