Migrate from package enumerate to enumitem for flexible itemize environments

[jemus42]

The itemize environment is provided by the enumerate LaTeX package, which according to the author has not seen a lot of development for 30 years (see this particularly salient comment)

The common recommendation (echoed by the enumerate author) is to use the enumitem package, see e.g. the documentation PDF here.

Notably the enumitem package does not provide backwards compatibility, so changing the preambles to usepackage{enumitem} rather than \usepackage{enumerate} breaks some lecture slides, e.g. in I2ML.

It would however give itemize envrionments more flexibility and be probably also more futureproof.
One way to tackle this would go to each lecture like I2ML, substitute enumerate -> enumitem, see which slides break with lecheck compile -l i2ml --preclean, fix the slides accordingly in a PR, and merge the PR once the style files in lecture_service/style/preamble.tex have been changed globally to use enumitem.

Then again, we are talking about touching running systems.