## Description
This fixes an issue in the creation of the `FocusScope` in a route: the route should be creating the `FocusScope` widget it has with `withExternalFocusNode`, since it is modifying the node attributes in a builder.
Also modified some `AnimatedBuilder`s to be `ListenableBuilder`s, since they're not using animations (no functionality change there, since the implementation of the two is identical).
## Related Issues
- #147256
- Fixes#146844
## Tests
- Updated example test.
