replace pyfilesystem2 by pathlib

Project description: The whole project needs to become refactored for replacing our usage of pyfilesystem2 by pathlib.
Duration: 175-350h
Skills: Python, flask, socketIO, pathlib, Git, AI-Assistant
Difficulty level: Medium
Related Readings/Links:
- https://github.com/Open-MSS/MSS/issues/2103
- https://github.com/Open-MSS/MSS/issues/2347
Potential mentors: j.ungermann@fz-juelich.de, rb.proj@gmail.com