Merged requested to merge pabloyoyoista/gnome-software:icon-sizes into main
And check for those before checking for other icons, since they are expected to be provided in any possible size.
Fixes #2063 (closed)
I put on top two additional commits, one with a more descriptive comment and another one with a small optimization. Maintainers tell if they should rather be dropped, what I really care about is the fix :)