Priority option for feeds

[gixxy22]

Would be nice to have an option to enter a priority for feeds, when multiple feeds are run on crons, it would be nice to prioritise some over others.

This would be especially helpful when there are feeds with pagination, as page 2 of a feed will end up running AFTER a different feed and everything gets a bit messy.

If priority was an option, the feed with pagination would always finish first before moving on to another feed, regardless of the queue ID.