camera2: Fix cts test StillCaptureTest#testTakePicture

* Introduce 'fake' metadata for 3A+flash (hardcoded to support nothing)
(will be removed in a later release)

* Open the camera1 device in its own thread, so that the looper it
captures is also our own (and not the main looper)

* Set the picture size based on the size of the JPEG surface outputs

Change-Id: Iaeb5031c6b352115b73d2261a39d65347d75fdc8