[enhancement]: mypy requires tox

# Enhancement

Various test dependencies are not included in our `test-requirements.txt`, which means that running outside of `tox` for certain tests (`mypy`, `hypothesis`), require digging in the `tox.ini` to get this dependency list. It would be nice for these to be grouped with the other unittest dependencies, or maybe in a separate dependency file (or even just in `pyproject.toml`).