Add test to avoid max recursion errors

[Telijas]

This PR adds one test to the new non recursive version of the Gomory Hu processing. A test was missing to show that no recursion error occurs.
The test gets the current max recursion depth of the system, creates a graph with a unique Gomory Hu tree (path here) and computes it.
The new version of Gomory Hu is added with sagemath#38791

📝 Checklist

• The title is concise and informative.
• The description explains in detail what this PR is about.
• I have linked a relevant issue or discussion.
• I have created tests covering the changes.
• I have updated the documentation and checked the documentation preview.

⌛ Dependencies

sagemath#38791

[dcoudert]

Hello, I just see this PR and I don't think it's the right place. Can you open a new PR on the main sagemath repository (https://github.com/sagemath/sage).