Move all poetry scripts to Taskipy tasks

https://github.com/illBeRoy/taskipy

taskipy enables us to run arbitrary scripts from poetry. Moving the remaining entry points into taskypiy will be nice because of a consistent syntax: `poetry run task xyz`

To-do:

- Add `taskipy` to dev dependencies
- Add `if __name__ == "__main__"` clauses to all modules that contain entry points
- Add tasks to `pyproject.toml`