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.

CRs-Fixed: 514199
Change-Id: I8b155e305a836729b071e5388a7046c6347bb9f3