Camera2: Add activity-based test

Below are added:
- Camera2StubActivity class, which uses SurfaceView to render the camera
output buffers.
- Camera preview test, which uses the Camera2StubActivity to do the preview
test for each camera and each supported preview resolution (up to 1080p).

Also cleanup some minor issues in ImageReaderTest.

Bug: 9802344
Change-Id: I2cf8f329aeb39eeb8b27a51b9f3e3ab3526f503c