When the StatefulSetMinReadySeconds feature gate is disabled,
the registry and validation must properly handle dropping the
minReadySeconds and AvailableReplicas fields
Implements history utilities for ControllerRevision in the controller/history package
StatefulSetStatus now has additional fields for consistency with DaemonSet and Deployment
StatefulSetStatus.Replicas now represents the current number of createdPods and StatefulSetStatus.ReadyReplicas is the current number of ready Pods
The alpha field podManagementPolicy defines how pods are created,
deleted, and replaced. The new `Parallel` policy will replace pods
as fast as possible, not waiting for the pod to be `Ready` or providing
an order. This allows for advanced clustered software to take advantage
of rapid changes in scale.
