chore: improve cucumber tests

[SWvheerden]

Description

[gemini-code-assist]

Code Review

This pull request refactors port management and cleanup logic in the integration test suite, specifically introducing a port pool for merge mining proxies and adding timeouts to the base node shutdown process. Feedback indicates that merge mining proxies lack a proper shutdown mechanism, which could lead to port conflicts when ports are re-allocated. Furthermore, the base node cleanup logic should be updated to provide a full timeout period for each individual port to avoid premature warnings.