fix: turn on power_devices associated with screen on startup (#1556)

if the screen was off and KS restarted it would have remained off, this should fix this issue

screen.py

@@ -1159,6 +1159,7 @@ class KlipperScreen(Gtk.Window):
         self.ws_subscribe()
 
         self.files.set_gcodes_path()
+        self.power_devices(None, self._config.get_main_config().get("screen_on_devices", ""), on=True)
 
         logging.info("Printer initialized")
         self.initialized = True