Camera2: Add support for partial result metadata quirk

- Add new CaptureListener.onCapturePartial() callback for receiving
  partial result metadata sooner than the full result metadata will be sent
  in onCaptureComplete().
- Add hidden keys for the partial result quirk
- Dispatch results to onCapturePartial based on the partial result quirk

All additions are hidden for now.

Bug: 11115603
Change-Id: Ie9a3be640f147257ae22e5b5edf0974bddc1cb85