conformance testing CI/CD support

[catkins-miso]

• refactor the devcontainer Dockerfile to have a dev and runtime/CI stage with a shared root dependency stage that lays down all the testing dependencies
• determine how best to accommodate pluggable model load and auth when using, e.g., inline files in runtime/CI stage, only env var https://github.com/trolie/conformance/blob/main/test/helpers.py#L157