Improve the Video RAM debugger UX

- Refresh tha tab automatically when switching to it.
- Disable the Refresh button if no project is currently being debugged.
- Scale the column widths on hiDPI displays.
- Rename the tab from "Video Mem" to "Video RAM" for consistency.

(cherry picked from commit 8f838f33b7)

editor/script_editor_debugger.h

@@ -226,6 +226,7 @@ private:
 
 	void _error_tree_item_rmb_selected(const Vector2 &p_pos);
 	void _item_menu_id_pressed(int p_option);
+	void _tab_changed(int p_tab);
 
 	void _export_csv();