Make socranop install/run with the 2023 toolchain

[ndim]

The first priority is to get a working environment for socranop both on my Python 3.12/Fedora 39 workstation and on Github's CI infrastructure in late 2023 so I can actually work on socranop again.

After that, we can make sure this also works back to whatever older Python and older tool versions we want to support.

This is a PR to have the CI tests available from the start, and then for review.

[ndim]

As it stands at https://github.com/socratools/socranop/commit/c0be720206b6bd25e49a5184d92ea9d383c28b8f, this

• successfully runs pre-commit run -a on my workstation, allowing me to git commit again
• successfully runs the socranop code on my workstation, so I can locally test socranop with my hardware
• successfully runs the CI checks on Github, so that I can create PRs to be merged

As myopic as I am, I do not expect any of the changes so far to break on systems with older toolchaings.

There are still a few code changes to be ironed out. E.g. when I change any of the *.py source files, flake8 will complain about a lot of things in the changed source file. This can be circumvented by either adding a lot of flake8 errors to the list to be ignored, or by fixing the code.