Make text-related nodes translation domain aware

- Makes `is_layout_rtl()` translation domain aware
- Makes various text-drawing controls translation domain aware
- Makes translation preview use the project's fallback locale when disabled

scene/gui/text_edit.h

@@ -332,7 +332,7 @@ private:
 	Array st_args;
 
 	void _clear();
-	void _update_caches();
+	void _update_caches(bool p_invalidate_all = false);
 
 	void _close_ime_window();
 	void _update_ime_window_position();