port hook commands missing --app option

The port related hook commands

open-port
close-port
opened-ports

should have an --app option similar to relation-set etc

For machine charms, each unit can separately call open-port etc. But for k8s charms, only the leader can call it and each unit gets the same ports.

So we need to provide --app to give the same experience as for relation-set et al.

For k8s, we will need to fail with an error message like "ports cannot be managed for individual units" if --app is not used.

For machine charms, --app is not (yet) supported so a error message is needed if --app is used.