gdebugcontrollerdbus: Add stop() method

This allows the controller to explicitly be removed from the bus, in a
way that allows the caller to synchronise with it and know that all
other references to the controller should have been dropped (i.e. after
this method returns, there should be no in-flight D-Bus calls still
holding a reference to the object).

This is needed to be able to guarantee finalisation of the controller in
unit tests (and comparable real-world situations).

Signed-off-by: Philip Withnall <pwithnall@endlessos.org>

Helps: #1190

gio/gdebugcontrollerdbus.h

@@ -61,6 +61,9 @@ GDebugControllerDBus *g_debug_controller_dbus_new (GDBusConnection  *connection,
                                                    GCancellable     *cancellable,
                                                    GError          **error);
 
+GLIB_AVAILABLE_IN_2_72
+void g_debug_controller_dbus_stop (GDebugControllerDBus *self);
+
 G_END_DECLS
 
 #endif /* __G_DEBUG_CONTROLLER_DBUS_H__ */