Rename CanvasItem.update() to queue_redraw()

Affects a lot of classes. Very thoroughly checked signal connections and deferred calls to this method, add_do_method/add_undo_method calls, and so on.

Also renames the internal `_update_callback()` to `_redraw_callback()` for consistency.

Just a few comments have also been changed to say "redraw".

In CPUParticles2D, there was a private variable with the same name. It has been renamed to `do_redraw`.

editor/plugins/node_3d_editor_plugin.h

@@ -433,7 +433,7 @@ protected:
 	static void _bind_methods();
 
 public:
-	void update_surface() { surface->update(); }
+	void update_surface() { surface->queue_redraw(); }
 	void update_transform_gizmo_view();
 
 	void set_can_preview(Camera3D *p_preview);