Switch to using pathlib

[zmievsa]

Goals

• [ ] The ruff pathlib checks are enabled. :information_source: In order to do that, edit the part of pyproject.toml marked as TODO#89.
• [ ] Calls to os.path are replace with pathlib.
• [ ] Reading and writing files is replaced with Path.read_text and Path.write_text where feasible.
• [ ] All TODO#89 comments are addressed.

Estimate: 8h

Original request

Many parts of the project can be both sped up (though insignificantly) and made more readable by replacing os usage with pathlib usage. File reading/writing can also be made more readable in some places using Path.read_text and Path.write_text. If you have time on your hands, I think investing into this idea would be a good improvement

[roskakori]

Yes, probably a reasonable cleanup at some point.