As discussed on https://issues.redhat.com/browse/OSPRH-11957 until we handle properly the scale down scenario, we need to make sure that decision-engine and applier are created with replica=1.

The best of implementing this is to add a validation rule in watcher webhook to make sure that the value for replicas for decision-engine and applier are always set to 1. Otherwise, the request should not be accepted.

Definition of Done:

A request to create a Watcher CR which sets replicas to > 1 in WatcherDecisionEngine or WatcherApplier is not accepted.