Camera2: State must be STOPPED before JPEG callback is fired.

Move handling of JPEG callback to CaptureSequencer instead of
JpegProcessor, so that we can be sure the camera state is updated to
STOPPED before the JPEG callback is sent to the application layer.

Bug: 7172743
Change-Id: Ie8752d946d3eb8254230c77f10e5c38a83dc5371