Factor out Velero synchronization to a separate process

[pbalogh-sa]

Describe the solution you'd like to see
Figure out, how the ARK syncing mechanism should work in order to get rid out of the sync goroutine.

#1609

[sagikazarmark]

The first step should be factoring out the synchronization to a separate process in an effort to make Pipeline HA. Refactoring Velero to work without synchronization is a bigger task.

[sagikazarmark]

Requires #3370