Support camera size selection using -m/--camera-ar

In addition to --camera-size to specify an explicit size, make it
possible to select the camera size automatically, respecting the maximum
size (already used for display mirroring) and an aspect ratio.

For example, "scrcpy --video-source=camera" followed by:
 - (no additional arguments)
    : mirrors at the maximum size, any a-r
 - -m1920
    : only consider valid sizes having both dimensions not above 1920
 - --camera-ar=4:3
    : only consider valid sizes having an aspect ratio of 4:3 (+/- 10%)
 - -m2048 --camera-ar=1.6
    : only consider valid sizes having both dimensions not above 2048
      and an aspect ratio of 1.6 (+/- 10%)

PR #4213 <https://github.com/Genymobile/scrcpy/pull/4213>

Co-authored-by: Simon Chan <1330321+yume-chan@users.noreply.github.com>