Extend output format with downscalable resolutions

Extends set of supported output formats with "standard"
resolutions with same aspect ratio as input which we can
downscale into.

Also fix bug, where the callback was always invoked with hardcoded
YUV format.

Add validation to ensure all streams in the session have same aspect
ratio (support for different ratios coming in follow-up).

Bug: 301023410
Test: atest virtual_camera_tests
Test: atest VirtualCameraTest
Change-Id: I42a46712c0b12e8a5ae3d75fa07e8f8ea47e8cc2