Add support for Python 3.12

[veenstrajelmer]

What is the need for this task.
Python 3.12, since this is GA since October 2023. Support should be added. Support for py310 was added in #586 and support for py311 was added in #598.

What is the task?

• add python 3.12 to ci.yml
• add python 3.12 to pyproject.toml (classifiers) >> not needed
• add python 3.12 to pyproject.toml (tool.black target-version) >> not supported yet (april 2024)
• locally run py3.12 testbank (conda env with pip+git installation from the linked branch) >> success, all test passed
• fix failing build: Note: This error originates from the build backend, and is likely not a problem with poetry but with pyzmq (24.0.1) not supporting PEP 517 builds. You can verify this by running 'pip wheel --use-pep517 "pyzmq (==24.0.1) ; python_version >= "3.6""'.
• when disabling poetry.lock, the error occurs elsewhere: Note: This error originates from the build backend, and is likely not a problem with poetry but with numpy (1.24.4) not supporting PEP 517 builds. You can verify this by running 'pip wheel --use-pep517 "numpy (==1.24.4) ; python_version >= "3.8""'. >> later, on 29 april 2024, we get this error for pyzmq (==24.0.1)"
• this is odd, since both packages support py3.12 according to their specs and the (closed) issues. However, for some unknown reason, poetry installs older package versions that do not support py3.12.
• try updating to abatilo/actions-poetry@v3 >> fails for macos-13 (and also the original fails), so alleviated to abatilo/actions-poetry@v2
• try updating to poetry-version: 1.8.2
• try disabling caching of env >> will probably not work since Cache not found for input keys: venv-windows-latest-3.12-
• error seems to originate form installation of widgetsnbextension, which is not available for py 3.12 according to pypi. Try to remove dependency that requires this package
• Update/add documentation for our supported python versions
• save some CO2: remove py310/py311 from ci.yml, we can probably safely assume that if py39 and py312 work properly, the inbetween versions also work properly. py38 is an exeption, since it is almost EOL and many packages do not provide new versions for py38 anymore.