Introduce composite action for running ping interop tests

[thomaseizinger]

This PR implements some of the ideas discussed in #111. It is intended to be fully backwards-compatible and can thus be rolled out incrementally across our repositories.

We do a few things here:

1. GitHub actions needs to already checkout the test-plans repository to access the action's source code. We can reuse this checkout to access the rest of the repository. Thus, if we reference this action via a commit hash, downstream repositories don't suddenly break on changes to the test-runner or other things in here.
2. Compared to the previous workflow, we don't cache the NPM dependencies. This is a technical limitation originating from (1) as GitHub refuses to cache things outside of $GITHUB_WORKSPACE. This doesn't really matter though as our runner has very few dependencies which are installed in no time.
3. Because this is now a composite action, we don't need to up/download any artifacts from the source repository. Instead we simply embed this action in a bigger workflow: https://github.com/libp2p/rust-libp2p/blob/test-composite-test-plans-action/.github/workflows/interop-test.yml.
4. extra-versions should be a space-separated list of JSON files that each contain a JSON object which describes a version to include in the matrix. See the changes to the JSON file in the rust-libp2p PR: https://github.com/libp2p/rust-libp2p/pull/3414/files
5. The support for extra-version in the test runner is backwards-compatible.
6. When building local docker images, repositories need to make sure that containerImageID exists locally. As you can see from the rust-libp2p PR, all that is needed is to build and tag the image locally. Because we are within the same workflow, the state of the local docker daemon is preserved.

[MarcoPolo]

Should we just replace the above?

[MarcoPolo]

I'm guessing the intent was to make sure the existing flow didn't break?

[thomaseizinger]

Yeah, it is always easy enough to just remove the above later once we are fully migrated.

[MarcoPolo]

This looks good.

After we merge this, I'm guessing the plan is to change {rust,go}-libp2p to use this composite action at the current commit. Then we can rollout the other changes?

[thomaseizinger]

This looks good.

After we merge this, I'm guessing the plan is to change {rust,go}-libp2p to use this composite action at the current commit. Then we can rollout the other changes?

Yep, that would be the idea!

[thomaseizinger]

After we merge this, I'm guessing the plan is to change {rust,go}-libp2p to use this composite action at the current commit.

I opened a PR for go-libp2p here: libp2p/go-libp2p#2039