Ephemeral volumes are not scheduled in the same zone as machines

[gonzolino]

Describe the bug
MCM allows to schedule machines in zones using topology-aware scheduling. However, attached ephemeral volumes are not always scheduled in the same zone. While this works technically, it increases the risk of failures because outages in both the machine zone and the volume zone may now affect the machine.

To Reproduce
Create machines with MCM, then check the machines and volumes and verify if machinepool and volumepool belong to the same zone. E.g.

$ k get volume my-machine-root -o jsonpath={.spec.volumePoolRef}
{"name":"az2"}
$ k get machine my-machine -o jsonpath={.spec.machinePoolSelector}
{"topology.ironcore.dev/region":"region1","topology.ironcore.dev/zone":"az1"}

Expected behavior
If available, topology-aware scheduling should be used for volumes as well.