chore: move to Python 3.11 (DEV-2524)

[jnussbaum]

No description provided.

[linear]

DEV-2524 move to python 3.11

Currently, DSP-TOOLS relies on Python >= 3.9. This has some disadvantages:

• The tests on GitHub CI run with Python 3.9, which is slower than 3.11, and produces less comprehensible error messages.
• The codebase of DSP-TOOLS cannot take advantage of newer syntax introduced in 3.10 / 3.11.

In the RDU team, we agreed that we can move to 3.11. We just have to inform Lausanne some days before the release, so that they know that they must have Python 3.11 on their machines.

The schedule to migrate DSP-TOOLS to Python 3.11 is as follows:

1. specify 3.11 in pyproject.toml and on https://pypi.org, so that the users with an older Python version cannot update DSP-TOOLS any more, and must install Python 3.11 first.
2. If step 1 works without problems, use new features

[BalduinLandolt]

Good! Now too long if-elif listings can be replaced with pattern matching :)