Remove the double kso_utils directory and adjust CI and pylint

[Diewertje11]

This PR removes everything from the old submodule that is not the actual code, and puts the code directly in the first kso_utils folder.

Then it corrects all the references for imports. And the references in the CI pipeline.

Lastly it integrates the pylint check into the build-and-test-docker. This is because we want to run them in an updated container. And since the NB-tests already open this container, it is added as a step in this job so that we do not need to do any steps double.

The pylint tests are added as separate steps for the kso_utils, the tests and the tutorials, since we need a different package (nbqa) to do pylint on the jupyter notebooks. These 3 will always run (due to the if success/failure statement). However, the actual notebook and widgets tests will only run when the pylint tests have passed. They do not need to run if we have detected errors with pylint.

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[Diewertje11]

I think that the python tests and CI are working as we expect.

The only 2 tings that I came across that are going wrong in the CI are:

• No new container is created when something is changed to the requirements, this I saw in the commit in dev where we updated the submodule.
• when nothing changes to any files and it is a pull request, we do not want to update, we can just pull in dev. But right now we updated the container. (Maybe this was because we want to update the code in the container, so this is solved as soon as we bring main back into the picture). But at least we need to double check if this works as we expect

But those things did not have anything to do with the changes in this PR. So if others have looked over it and don't see anything strange, it is ready to be merged.

[Diewertje11]

I did not squash the commits, since we then need to wait for the CI checks again. But since the PR will squash it anyway and there are not that many if you look into the PR separate, I hope that this is not a problem.