I need a nox session in the Python library templates that allows us to install pre-release dependencies. It requires the following information:

• Package names to install a pre-release. e.g. grpcio, google-api-core, google-resumable-media (though some of these might be there by default)
• Extra index URL (if needed), such as "https://pypi.fury.io/arrow-nightlies/" for pyarrow and "https://pypi.anaconda.org/scipy-wheels-nightly/simple" for pandas/numpy
• How to get to __version__ to print for debugging of which pre-release was installed. e.g. session.run("python", "-c", "import grpc; print(grpc.__version__)"). Alternatively, maybe the session just needs a pip freeze?

Related: We might want to remove the grpcio pre-release from the normal system test session.

Context

See:

• Client libraries need out-of-band tests against prereleases of third party dependencies google-cloud-python#10578
• Python: refactor installing unit/system test dependencies #1185
• Integration test with pyarrow nightly builds? python-bigquery#95
• support google-cloud-bigquery 3.x (test with pre-release dependencies) python-bigquery-pandas#426