This PR does two things:
- Only run the tests when relevant files change.
- Cache the Go Modules directory between runs, so they don't have to redownload everything everytime (go.sum is the cache key). Pretty much straight from the examples: https://github.com/actions/cache/blob/master/examples.md#go---modules
This change adds a new Github Action, a 3 node smoke test. It starts
three docker containers (one lighthouse and two standard nodes) and
tests that they can all ping each other. This should hopefully detect
any basic runtime failures in PRs.