periodic recheck of reviews

Some reviews in gerrit hang out for a while before they are finally approved. Typically after 3 or 4 days the patch could no longer be automatically merged because changes have happened below it that doesn't let it get rebased.

It would be a "nice to have" feature to have a periodic job that goes through reviews every couple of days when the system is idle and rechecks them. This would give the author an indication that they need to rebase early, instead of it finally getting to a +2 + Approved state, then it failing on the merge, and having to collect the +2s all over again.

I've been manually triggering "recheck" in patches that are long in the queue recently to indicate that, but would be great if the system did it automatically.