tests: add proxy option to test file for driver

[DnPlas]

Adding a proxy option to the driver/test_kubeflow_workloads.py script, will allow users to tell the driver it will run in a proxied environment. With this, a PodDefault will be used for setting environment variables (NO_PROXY, HTTP_PROXY, HTTPS_PROXY) in the Pod(s) that execute the Job for UATs.

Fixes #96

Manual testing

1. Deploy juju deploy admission-webhook --channel 1.9/stable --trust
2. Deploy juju deploy kubeflow-profiles --channel 1.9/stable --trust
3. Clone this repository and checkout to the branch git checkout KF-6029-configure-driver-behind-proxy
4. Run the UATs with proxy tox -e uats-local -- --proxy http_proxy=daniela:9090 https_proxy=daniela:9090 'no_proxy=no,proxy,comma,separated'
5. Verify the Pod created by the UATs Job has the desired Environment vars:

$ kubectl describe pod -ntest-kubeflow test-kubeflow-*
...
    Environment: <--- all of these should match the ones in the PodDefault from (4)
      HTTP_PROXY:   daniela.io:9090
      http_proxy:   daniela.io:9090
      HTTPS_PROXY:  daniela.io:9090
      https_proxy:  daniela.io:9090
      NO_PROXY:  no,proxy,comma,separated
      no_proxy:  no,proxy,comma,separated
...

6. Alternatively, you can check the admission webhook logs to ensure it is applying the PodDefault correctly:

$ kubectl logs -nkubeflow admission-webhook-0 -cadmission-webhook -f
...
2024-08-19T08:28:42.507Z [admission-webhook] I0819 08:28:42.507864      14 main.go:600] Entering mutatePods in mutating webhook
2024-08-19T08:28:42.516Z [admission-webhook] I0819 08:28:42.516173      14 main.go:646] fetched 1 poddefault(s) in namespace test-kubeflow
2024-08-19T08:28:42.516Z [admission-webhook] I0819 08:28:42.516199      14 main.go:662] 1 matching pod defaults, for pod 
2024-08-19T08:28:42.516Z [admission-webhook] I0819 08:28:42.516206      14 main.go:668] Matching PD detected of count 1, patching spec
2024-08-19T08:28:42.516Z [admission-webhook] I0819 08:28:42.516216      14 main.go:481] mutating pod: 
2024-08-19T08:28:42.516Z [admission-webhook] I0819 08:28:42.516227      14 main.go:683] applied poddefaults: notebook-proxy successfully on Pod:  

[NohaIhab]

thx @DnPlas, I followed the test and instructions and was able to see the proxy envs set in the pod created by the Job, looking good already. Left a few comments.

[NohaIhab]

a few more comments, looking good already (:

[NohaIhab]

LGTM, Thx @DnPlas !