ci: run tests-py3 jobs on v2.0 images We can't use v1.0 images because they still have Python 3.7. Let's switch to using pip to install the extensions to avoid a SetuptoolsDeprecationWarning about running setup.py directly. This also avoid the warning about python_requires apparently. The "running as root" warning cannot be simply avoided by using a different CI image. We do have v2.1 images that default to ci-runner user, but no one forbids people from running the test locally as a root user, one way or another. Running pip as root shouldn't matter in this case, since it's not a real system install, so this particular warning is always irrelevant.