Support Docker Compose as environment description

[yorugac]

Currently xk6-environment supports description via Kubernetes manifests and vcluster. That's not the only way to describe the environment and while we shouldn't aim to support all of them, it makes sense to consider the Docker Compose. It is used rather frequently as an alternative "environment description" to Kubernetes.

This will require a full re-implementation of all functionality, with another implementation in definition:

const env = new Environment({
  name: "some-name",
  implementation: "docker-compose", // <-- new kind here
})

Function signatures would also need to be considered carefully. For example, wait function might take a somewhat different form as a result: with another set of fields specific for Docker Compose, and so on.