core/server: add generic dbus service

- Add QML client with subscribe/introspect/getprop/setprop/call
- Add CLI helper `dms notify` that allows async calls with action
  handlers.

core/cmd/dms/commands_common.go

@@ -511,6 +511,8 @@ func getCommonCommands() []*cobra.Command {
 		colorCmd,
 		screenshotCmd,
 		notifyActionCmd,
+		notifyCmd,
+		genericNotifyActionCmd,
 		matugenCmd,
 		clipboardCmd,
 		doctorCmd,