Conformance tests: optional connectivity tests for conflicting ports

[MrFreezeex]

Add optional connectivity test(s) corresponding to this part of the KEP in https://github.com/kubernetes/enhancements/tree/master/keps/sig-multicluster/1645-multi-cluster-services-api#service-port:

In that case, network traffic to a conflicting port should
only be directed to endpoints from constituent services that actually expose the port.

The two following tests might be interesting:

• cluster1 (oldest): svc ports: name:tcp port: 42 / cluster2 svc ports: name:tcp port: 4242 (same name but conflicting port) -> check that reaching port 42 should only get to cluster1
• cluster1 (oldest) svc ports: name:tcp port: 42 / cluster2 svc ports: name:tcp2 port:4242 (port union) -> check that reaching port 42 should only get to cluster1 and that reaching port 4242 only reach cluster2