Update to new Nox

[theacodes]

Nox recently made a big change from declarative to imperative and broke the Noxfile API.

We need to update our Noxfiles to work with the new API and update our test scripts to install nox (instead of nox-automation) and invoke python3 -m nox {args}.

Most projects just need to do a few steps:

1. Remove usage of session_{name} sessions and use @nox.session instead.
2. Don't use session.interpreter, use @nox.session(py='...')
3. Don't use nox.parametrize for multiple Pythons, use @nox.session(py=['..', '..']).

[engelke]

Handled in PR #1770.