Using default nodePort in tests in unreliable because it might already be occupied on CI

### Problem statement

Using a concrete, default `nodePort`: https://github.com/Kong/kubernetes-testing-framework/blob/238e12e74d32e8692fcae1435b45fd8490f70ac9/pkg/clusters/addons/kong/addon.go#L540 proves to be unreliable in tests, especially in CI since we don't have full control over the environment and sometimes the port can be already occupied e.g. https://github.com/Kong/kubernetes-testing-framework/actions/runs/5022546754/jobs/9006138317#step:8:144 which fails the test.

### Proposed solution

Use something like `github.com/phayes/freeport` which allows finding a free port and use that in tests.

Start at pkg/clusters/addons/kong/addon.go around line 540 and inspect the tests that use the concrete default nodePort. Evaluate the proposed free-port approach, then run the affected integration tests; done means they no longer fail when that port is already occupied in CI.

Written by the indexing model from the issue text.