testing/megapixels: upgrade to 0.9.0, move to community
Set arch to all, as it builds for more than just ARM and the author (Martijn) doesn't plan to make it ARM specific forever. We'd like to ship this as default in postmarketos-ui-phosh, which is easier with arch=all as well.
(Done as two commits, let me know if having it in one commit would be preferred.)