[Feature]: Replace `setup.py` with `pyproject.toml` for modern Python packaging

[tomvothecoder]

Is your feature request related to a problem?

Refer to xCDAT/xcdat#712 for more info on what to do.

Describe the solution you'd like

• Move setup.py configs to pyproject.toml
• Delete setup.py and remove line in tbump.toml

Describe alternatives you've considered

No response

Additional context

No response

[tomvothecoder]

closed by #895