Get outdated repositories from the replication queue

Adds GetOutdatedRepositories to the replication queue. This is useful for determining data loss cases and for deciding which nodes need repairing.

The following criteria apply when determining out of date repositories:

1. Source is the reference node and the state is not 'completed'. Having uncompleted job from the reference indicates unreplicated writes.
2. Source is not the reference and the state is 'completed'. If the job is not 'completed', the secondary's state has not been replicated to the node. We then take the next job from the reference node or the next completed job.

Repository is only considered up to date if has been directly replicated from the reference storage. Repository that is up to date by replicating from an up to date secondary is not considered up to date. The source node must be the previous writable primary.

This commit only adds backstage changes and the code is not in use yet.

Relates to #2683 (closed)