Migrate PodDisruptionBudget to policy/v1

Move PodDisruptionBudget from policy/v1beta1, removed in Kubernetes 1.25, to policy/v1, adjusting an empty spec.selector so the budget goes on covering the same pods. Under policy/v1beta1 an empty selector ({}) selected no pods; under policy/v1 it selects every pod in the namespace, so changing only the API version would silently turn a budget that did nothing into one that blocks every eviction in its namespace. An unset selector means "no pods" in both versions, so the empty selector is dropped rather than carried over.