Keep internal Nexus pod alive when K8s scales down

Since the Kubernetes cluster upgrade to 1.22, the "ScaleDown" event deletes the Nexus pod, which then takes a long time to restart due to "Unable to attach or mount volumes".
This is blocking the CI jobs with errors such as:

Connect to nexus:80 [nexus/10.63.255.85] failed: Connection refused (Connection refused)

ScaleDown events:

k get events --sort-by='lastTimestamp' | grep "deleting pod"
7m17s       Normal    ScaleDown                pod/nexus-84f644b8f8-lnnzs                                      deleting pod for node scale down
...

See https://cloud.google.com/kubernetes-engine/docs/concepts/cluster-autoscaler

In GKE clusters with control plane version 1.22 or later, Pods with local storage no longer block scaling down.

Possible fix: adding the following annotation to the Nexus pod:

"cluster-autoscaler.kubernetes.io/safe-to-evict": "false"

See https://cloud.google.com/kubernetes-engine/docs/how-to/cluster-autoscaler-visibility.

Also see NXBT-3604 and possible fix https://github.com/jenkinsci/helm-charts/blob/main/charts/jenkins/README.md#long-volume-attachmount-times.