Not everything that responds to `routes` is a Rails engine - for example
a Grape API endpoint will have a `routes` method but can't be used with
`assert_recognizes` as it doesn't respond to `recognize_path_with_request`.
Fixes#32312.
Before this commit paths of mounted engines are not traversed
when `assert_recognizes` is called, causing strange test results.
This commit enable to traverse mounted paths.
