PodDisruptionBudget for DT ActiveGate

[wiegandf]

Since the activegate is a component that teams would like to run in high availability mode, there should be a pod disruption budget to ensure there's always one activegate up and running.

The operator could create a pdb once replicas are set > 1.

[jmdoherty]

And pod topology spread constraints, similar to how: https://docs.dynatrace.com/docs/setup-and-configuration/setup-on-k8s/guides/high-availability/high-availability functions.