Publish ipv6 in Theia connection parameters and in shell

For developers in Theia, launching a server (Django, Hugo, etc.) requires the ipv6 of Theia instance. But the only way to get it is to use slap-configuration in an instance, so we cannot get it outside the instance. So, it increases the complexity to launch a server, whereas we could get it with Theia's connection parameters or with an environment variable.