feat(interop-tests): use multistage builds to reduce final image size

[thomaseizinger]

Description

Once we ship libp2p/test-plans#161 or something like it, we should update our Dockerfile for the interop tests to use multistage builds.

Once that is done, we need to update the commit hashes in all these makefiles to a new commit for each version where the Dockerfile is using the multistage build.

Motivation

Faster CI because smaller images are quicker to download.

Are you planning to do it yourself in a pull request?

Yes if nobody beats me to it.