How to categorize this issue?
/area control-plane-migration
/area backup
/area disaster-recovery
/kind bug
/platform openstack

What happened:
Control plane migration did not succeed when server groups are used.

task "Waiting until worker resource status is updated with latest machine deployments" failed: Error while waiting for Worker shoot--staging--test/test to become ready: Error restoring Worker: failed to generate the machine deployments: server group is required for pool "worker-wh8of", but no server group dependency found

What you expected to happen:
Migrated control plane

How to reproduce it (as minimally and precisely as possible):
specify

        providerConfig:
          apiVersion: openstack.provider.extensions.gardener.cloud/v1alpha1
          kind: WorkerConfig
          serverGroup:
            policy: anti-affinity

in a shoot and migrate it to another seed

Anything else we need to know?:
thoughts:

• use predictable server group name
• persist providerconfig in shootstate

Environment:
openstack

• Gardener version (if relevant):
  1.132.2
• Extension version:
  1.51.0
• Kubernetes version (use kubectl version):
  1.33.6