## Issue Addressed
#2335
## Proposed Changes
- Remove the `lighthouse-network::tests::gossipsub_tests` module
- Remove dead code from the `lighthouse-network::tests::common` helper module (`build_full_mesh`)
## Additional Info
After discussion with both @divagant-martian and @AgeManning, these tests seem to have two main issues in that they are:
- Redundant, in that they don't test anything meaningful (due to our handling of duplicate messages)
- Out-of-place, in that it doesn't really test Lighthouse-specific functionality (rather libp2p functionality)
As such, this PR supersedes #4286.
b29bb2e037