Move MaxReplicas and MinReplicas to AutoscalerSpec in collector CRD

[moh-osman3]

In #1077, an Autoscaler field and object was added to the collector CRD. MaxReplicas and MinReplicas are fields specific to autoscaling so that should be moved to the AutoscalerSpec, and the HPA source code should be refactored to reflect this.

[pavolloffay]

cc) @kevinearls

[pavolloffay]

Also note that we can't remove fields from a published CRD. If we want to move things around we would have to do deprecation and support the deprecated options as well.