Run tests using a simpler image

[phoevos]

Currently, we run the tests using the following image:

charmed-kubeflow-uats/driver/test_kubeflow_workloads.py

Line 20 in 53e0389

TESTS_IMAGE = "kubeflownotebookswg/jupyter-scipy:v1.7.0"

The above is the default image used when creating a Jupyter Notebook on Kubeflow, and it was used to ensure the most straightforward path between testing/developing the example notebooks from inside a Notebook server to actually running these as part of the UATs.

This image, however, comes with many packages installed, most of which aren't of any use when it comes to running the UATs. At the same time, it can tie the UATs indirectly to a specific Kubeflow version.

Goal

Although the above are not critical, it's worth investigating the use of a leaner image, where we manually install only the necessary dependencies.

[phoevos]

Closing and reopening to trigger Jira automation.