Dockerize tests for reproducibility

[alxdavids]

Comment from @gpestana:

Dockerize tests for reproducibility across platforms (+ eventually run E2E locally for manual tests)

[rillian]

To clarify from offline discussions, the idea here is to provide a docker-compose.yaml or similar, along with container images built and uploaded to a registry, which describe how to stand up all the necessary services for an end-to-end test of the code. This makes it easy to get started examining the system design regardless of host platform.

I'm not sure this applies to the code in this repo, which as a library mostly relies on unit tests which call the relevant routines without an intervening network interface. One possible exception is the example randomness client and server.

It's definitely a good idea for downstream repositories which do implement network clients and services on top of these crates.