Allow to configure auto scaling

[corvus-ch]

• Create a ClusterAutoscaler object and provide parameters to control its behaviour.
• Create a MachineAutoscaler for each of the created MachineSets
• Replace replicas with replicas.min replicas.max.
• Defaults for replicas.min and replicas.max should be 1. This disables auto scaling by default, making enabling it a conscious decision.
• Do not longer set the replicas field on the MachineSets. It will be controlled by auto scaling and would confuse ArgoCD.