Randomize order of apps in queue to build

Recently, there were issues with fdroidserver getting stuck: #1094 (closed)

One app kept locking up the server. While most apps built fine, apps being in the queue after the broken app got delayed a lot. Organic Maps for example suffered from 18 days of delay (January 25 release of 2023.01.25-3-FDroid didn't get published until February 12th, after @jspricke disabled the app which made the server get stuck on February 10th).

I think it would be great to randomize the build order in the build queue, so that if an issue like this happens again, eventually all apps will be build anyway, instead of a few unlucky apps never getting built.