Wrapping one `WidgetAnimator` in another `WidgetAnimator` can cause issues

[andrewpmoore]

If one WidgetAnimator is wrapped in another then if there's a change to the lower level one it won't re-render (unless the key changes on the parent one), but a change of key on the parent widget means that any outgoing effects won't trigger.

At the moment a stack would need to be used to try and simulate one WidgetAnimator in another