switch to PDM, rm nox

[sneakers-the-rat]

Poetry and I have fallen out of love, and it will especially hold us back once we want to start doing compiled extension modules.

Should be no functional change here, and wherever you were using poetry before just swap it out to pdm.

e.g.

# install 
pdm install
# or (from a venv)
pip install -e .

# run `mio` cli
pdm run mio
# or, if installed in an activated venv, still just
mio

# run tests
pdm run test
# lint
pdm run lint
# format
pdm run format

# add dependency
pdm add package_name

[coveralls]

coverage: 74.603%. remained the same when pulling 1e3ad63d4d66612d905584e82571b113942ce2de on pdm into d4e45971db290bee72cbfbaf7a86cd214b8279de on main.