Reconsider dependency groups

[mfisher87]

Right now we only have a dev group. In that group, many things are listed, ranging from testing to docs to linting. IMO, we should have a dev group which includes only dev tools like pre-commit and Nox which are capable of managing their own environments. Then we can have two more groups: docs for mkdocs and friends. test for pytest, mypy, and friends. We can then use nox to handle running tasks like building docs, typechecking, and testing. Pre-commit handles everything that doesn't require the project's dependencies, like linting and formatting and various miscellaneous safety checks.

Regardless of whether we use Nox, I think it will be valuable to break out these 3 groups. More discussion here! #614