fix Rails.application.routes.router.visualizer for router debugging

[sfaxon]

Summary

In the Journey router the method Routes#partitioned_routes was removed, while Router#partitioned_routes depended on it. This moves the previous Routes#partitioned_routes logic into Router#partitioned_routes.

Other Information

To replicate the current bug just launch an app and call:
Rails.application.routes.router.visualizer

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[rafaelfranca]

Thanks. Backported in 4243a31