add k8s integration test harness

[zzstoatzz]

new k8s integration_tests package

» tree --gitignore src/integrations/prefect-kubernetes/integration_tests
src/integrations/prefect-kubernetes/integration_tests
├── README.md
├── pyproject.toml
└── src
    └── prefect_kubernetes_integration_tests
        ├── __init__.py
        ├── scenarios
        │   ├── __pycache__
        │   ├── base.py
        │   ├── eviction.py
        │   └── run.py
        └── utils
            ├── display.py
            ├── k8s.py
            └── prefect_core.py

see new CI job: https://github.com/PrefectHQ/prefect/actions/runs/13684789569/job/38265556186?pr=17385

[desertaxle]

This is great!