No support for multiple network devices at the same time

We need support for multiple network devices at the same time. We have been slowly working towards making network drivers more modular, which should help with this, but we need to make a final push for this.

Enabling multiple different drivers at the same time would be a natural extension of this effort, which would make Clippy runs much easier, but this is not of immediate need.

Start by reviewing the network-driver modularization work mentioned in the issue and how the current driver setup handles one device. Done means supporting multiple network devices at the same time, including different drivers, while making Clippy runs easier; the issue names no files or tests.

Written by the indexing model from the issue text.