Add support for DCT-unaligned JPEG compression.

This cl adds ability to specify viewport before rendering to buffer
and makes sure that the buffer always includes necessary padding
when rendering into buffer used for JPEG compression.

Bug: 301023410
Test: atest virtual_camera_tests
Test: Manually examining unaligned-sized thumbnails using exiftool
Change-Id: Id20cde4633ae396be9f9e8f9422b28d2b1475740