campaigns: Attempt to republish failed changesets

Created by: LawnGnome

A couple of random thoughts that occurred while I was working on this that I'd appreciate feedback on:

1. CreateChangesetJobForPatch arguably doesn't capture what the function now does, but I'm not sure what verb is more appropriate. QueueChangesetJobForPatch, maybe? I've updated it to Queue..., but would still welcome feedback on this.
2. More broadly, I'm not sure that having a unique constraint on changeset_jobs over campaign_id, patch_id makes total sense — is there any value to retaining failed jobs and their associated errors, or is this transient enough that we're OK with the "reset the fields and try again" approach in this PR?

Fixes #10795 (closed).