As part of the feature, users can now specify predefined MAC addresses for pods using the `v1.multus-cni.io/default-network` annotation.  OVN-Kubernetes must detect and prevent conflicts between:

• Requested addresses and existing allocated addresses
• Requested addresses and OVN-Kubernetes infrastructure addresses
• Multiple pods requesting the same addresses

We need to ensure that the conflict is clearly shown to the user, most likely using pod events.

OKEP reference: https://github.com/ovn-kubernetes/ovn-kubernetes/pull/5238