Add support for scheduleGroups

[mikkeloscar]

This extends the autoscaler.clusterScalingSchedule type with scheduleGroups support as introduced in zalando-incubator/kube-metrics-adapter#932

It allows opting in to a subset of scheduleGroups for a schedule like this:

autoscaler:
  metrics:
    - type: ClusterScalingSchedule
      average: 200  # 50 Pods as 10k/50 = 200
      clusterScalingSchedule:
          name: "schedule-x"
      # new feature:
      scheduleGroups:
      - cyber-week

which is translated to the underlying HPA with this config:

metrics:
  - type: Object
    object:
      describedObject:
        apiVersion: zalando.org/v1
        kind: ClusterScalingSchedule
        name: "schedule-x"
      metric:
        name: "schedule-x"
        selector:
          matchExpressions:
          - key: schedule-group
            operator: In
            values:
            - cyber-week
      target:
        type: AverageValue
        averageValue: "200"

[mikkeloscar]

👍