wayland: Hide XdgOutputV1Interface class
With the pull approach, the XdgOutputV1Interface class doesn't have to be exposed in the public api and can be made private to simplify the implementation of the xdg-output-v1 protocol.
With the pull approach, the XdgOutputV1Interface class doesn't have to be exposed in the public api and can be made private to simplify the implementation of the xdg-output-v1 protocol.