Restore script DBus API
The Script class has a DBus API we want to export. At some point this has got broken and the run method is not exported. It's a bit messy with script subclasses also having other invokables that we want to export to scripts, so an adaptor is used to keep things separated. The interface name has technically changed, but KWin was doing something weird and using the same interface names for the manager. Fortunately calling Plasma code doesn't specify an interface so this still works.