Our consoles currently miss the functionality

1. Add VNC console if missing
2. Edit address and port of the VNC console

Current plan:

• We add information about the VNC console to the "Consoles" card of a stopped machines: Whether there is one, and if so, listening address and port.
• We add "Add" and "Edit" buttons to the appropriate place next to that information which launch dialogs.
• For a running machine without VNC, we keep the VNC console in the dropdown but instead of showing the viewer, we show informational text stating that VNC can be added after stopping the virtual machine.
• The dialogs for adding and editing the VNC config allow setting of the listenting address and port, and password.

We restrict this to stopped machines to not make this task dependend on larger UI rework. We need that larger rework to find a nice place for the "Edit" button when the machine is running, see COCKPIT-1225.