Add option to force size alignment

Add --min-size-alignment to force a minimal size alignment.

This is a power-of-2 value (1, 2, 4, 8 or 16) that the video width and
height must be multiples of.

The actual alignment will be the maximum of this value and the video
codec's alignment requirement.

PR #6746 <https://github.com/Genymobile/scrcpy/pull/6746>