quickSettings: Rename 'label' property to 'title'

We'll soon add a subtitle, so rename the label property to something
that is a bit more semantic.Add a warning when trying to set the old
'label' property.

Part-of: <https://gitlab.gnome.org/GNOME/gnome-shell/-/merge_requests/2619>

js/ui/status/autoRotate.js

@@ -11,7 +11,7 @@ class RotationToggle extends QuickToggle {
         this._systemActions = new SystemActions.getDefault();
 
         super._init({
-            label: _('Auto Rotate'),
+            title: _('Auto Rotate'),
         });
 
         this._systemActions.bind_property('can-lock-orientation',