Update supported Python versions

[RobertoRoos]

Currently:

• The Gitlab CI is tested with Python 3.7 to 3.10.
• Black is configured to work on Python 3.7 to 3.10
• pyproject.toml / setup.py / setup.cfg

I would suggest we drop support for Python 3.7 and lower (deprecated since June 2023) and adjust everything to Python 3.8 to 3.12.