Side question. Do you think this should be an extra test? Is there any chance this can be a non-extra one?

Since this is a libp2p compatibility test, I'm leaning towards this being an extra test like the other compatibility tests such as tor, tgen, golang, the examples, etc. And then leaving the default tests to be just system call tests and other small tests. We do run all extra tests in the CI though, so any changes that break your libp2p tests would be caught before merging any future PRs.

This PR adds quite a few dependencies to the tests (from 207 to 341 compilation units) and increases the build time of the tests from 65 seconds to 99 seconds.[1] Shadow's build time is already painfully long, so I think it would be best to avoid increasing it by a lot in the default case unless there's a strong argument for it.

For users that want to run only the libp2p tests, they should be able to use ./setup test --extra libp2p.

[1] If #3304 is applied (both to shadow and this PR), the compilation units increase from 150 to 285 and the build time increases from 42 seconds to 71 seconds.

@stevenengler Since the epoll PR and netlink PR have been merged, do you have a plan for this PR?

I opened a discussion post about building the extra tests at #3305.