[Feature] Divide the Druid controllers into Reconciler and Actuator

[abdasgupta]

Feature (What you would like to be added):
To improve the readability of the druid controllers, we need to divide each controllers in two parts - reconciler and Actuator.

• The "reconciler" is responsible for reading the object that is being reconciled, managing finalizers, annotations, and status updates, and making the distinction between reconciling a creation / update (what we call "reconcile") and reconciling a deletion (what we call "delete"). Reconciliation logic is usually similar / generic and so often the same reconciler can be used with different actuators - but even if this is not the case, the distinction is still useful.

• The "actuator" is responsible for the actual reconciliation / deletion logic and returning an appropriately updated status (but not actually updating it).

For more details, follow the conversation : #235 (comment)
Motivation (Why is this needed?):

Approach/Hint to the implement solution (optional):

[abdasgupta]

cc @stoyanr

[unmarshall]

see #235 (comment)