Reconcile Consumer's CGs using declarative API

[czeslavo]

Problem Statement

As a stopgap before the 1.4 release, we used the existing imperative APIs (list + add/remove) to reconcile KongConsumer's ConsumerGroups with Konnect. There are plans to expose a declarative interface that should enable us to make these associations be propagated in just one call instead of multiple adds/removes.

Proposed Solution

Instead of calculating a difference between the actual and desired consumer groups' assignments, use the new declarative API.

Additional Information

Upstream API work is tracked under https://konghq.atlassian.net/browse/KOKO-1952.

Acceptance Criteria

• When a KongConsumer defines it belongs to multiple ConsumerGroups, this is propagated to Konnect in no more than one declarative call