Extend the CI coverage to test secondary networks on CAPO clusters

Add CI testing for secondary networks on CAPO, it seems not tested, an issue impacting workload clusters like #3408 (closed) was not spotted in CI tests.

Values that could be used are (helping to test also setting security groups and allowed address pairs):

cluster:
  control_plane:
    network_interfaces:
      secondary:
        network:
          id: <openstack_network_id> # existing network in Openstack with no gateway configured
        vnicType: normal
        securityGroups:
          - filter:
              name: "SG1" # existing security group
          - filter:
              name: "SG2" # existing security group
        allowedAddressPairs:
        - ipAddress: <aap_IP1>
        - ipAddress: <aap_IP2>
  machine_deployments:
    md0:
      network_interfaces:
        secondary:
          network:
            id: <openstack_network_id> # existing network in Openstack with no gateway configured
          vnic_type: normal
          securityGroups:
            - filter:
                name: "SG3" # existing security group
            - filter:
                name: "SG4" # existing security group
          allowedAddressPairs:
          - ipAddress: <aap_IP3>
          - ipAddress: <aap_IP4>