Make Pod SecondaryNetwork IP visible

[luolanzone]

Since we plan to promote SecondaryNetwork feature to Beta, it would be nice to provide a user-friendly way to let users to know what's the IP assigned to the secondary interface. We probably can add an annotation to the Pod and update the assigned IP to it when the Pod is created with secondary network interface successfully.

Not sure if we already report the assignment success or failure status to a Pod. if not, we may do another improvement to show the secondary IP assignment status in Pod's status?

[luolanzone]

cc @tnqn @antoninbas @jianjuns

[tnqn]

We should use k8s.v1.cni.cncf.io/network-status annotation to report the secondary network status, following https://github.com/k8snetworkplumbingwg/multus-cni/blob/4a0b5073afa53b57eb910896e72891d6857c199b/docs/quickstart.md?plain=1#L197, since we already follow it to define the secondary network spec via k8s.v1.cni.cncf.io/networks