CI: extend mypy and formating checks to include discopop_wizard

[lukasrothenberger]

Currently, only the explorer and profiler are covered by CI checks for type correctness and code formatting.

• Extend the CI Workflow to cover the wizard as well.
• Apply automatic formatting to wizard (python -m black -l 100 discopop_wizard)
• Fix potential typing errors in wizard detected by mypy (python -m mypy -p discopop_wizard)

[goerlibe]

all done already, except for ci formatting of wizard, which is done in #405