Added TopologySpreadConstraints support to ActiveGate spec

[mjgrzybek]

Description

Dynakube supports settings TopologySpreadConstraints for ActiveGate pods.

How can this be tested?

This dynakube should work and replicas should be spread across different nodes, if available:

apiVersion: dynatrace.com/v1beta1
kind: DynaKube
metadata:
  name: dk
  namespace: dynatrace
spec:
  apiUrl: <api_url>
  activeGate:
    capabilities:
    - kubernetes-monitoring
    - routing
    replicas: 3
    topologySpreadConstraints:
    - maxSkew: 1
      topologyKey: topology.gke.io/zone      # depending on your environment
      whenUnsatisfiable: ScheduleAnyway
      labelSelector:
        matchLabels:
          app.kubernetes.io/component: activegate
          app.kubernetes.io/name: dynatrace-operator
          app.kubernetes.io/created-by: dk

Checklist

• Unit tests have been updated/added
• PR is labeled accordingly