After got the proposal#35 accepted, we have to implement the corresponding logic for allowing a proper cluster rebalancing on scale up and down operations.

First of all, we need to extend the KafkaRebalance CRD supporting multiple mode for a full rebalance, adding and removing brokers.

After that, we need to add the logic in the KafkaRebalanceAssemblyOperator to handle these modes (where the full-rebalance is the current one).