Draft: vivian: default to using the latest valve-infra-container
Up until now, we have been asking people to create their own valve-infra-container images, which can then easily get outdated.
Rather than requiring running vivian from a local registry, let's just depend by default on the "upstream" container, then provision it with the latest changes using ansible.
It remains possible to use a local container by setting the IMAGE_NAME to localhost:8088/valve-infra/valve-infra-container:latest. This remains documented, but won't be the default.
TODO:
- Update the documentation to be clearer as to what the workflow should be