Tezt_cloud.Artifact_helperslocal_path path ensures that the path (as a list of subdirectories) is a valid directory, creates it otherwise, then returns the path. If the first directory starts with `/`, it will start from the root of the filesystem.
val prepare_artifacts :
?scenario_config:(string * Data_encoding.json) ->
unit ->
unitprepate_artifacts ?scenario_config () ensures the `Tezt_cloud_cli.artifacts_dir` is a valid dir (and creates it if needed), and push the full configuration in it.