Use e2e tests in the UI

We can run e2e tests that allow us to test things like components being mounted/unmounted, DOM changes, events, and other things that would be difficult to do with just unit tests, karma, qunit, jest, etc.

I used Cypress + offline data in the past. The offline data was served with a json-server and saved JSON data, used both for e2e tests and for quick prototype and development. Maybe we could use something similar.

There are alternatives to Cypress, like Nightwatch and Selenium too.

One thing that blocks this issue right now, I think, is the necessity to have a worker with these tools in GitLab. As far as I recall, our single worker is a VM with a shared Conda environment, used mainly/exclusively for Autosubmit Python. Messing up with that might break the worker and Autosubmit (as I did some months ago).