Update docstrings in inference modules to prettify the API docs

[ludovico-lanni]

Currently API docs for the inference modules (like https://david26694.github.io/cluster-experiments/api/variant.html) are not as pretty as those for power modules (like https://david26694.github.io/cluster-experiments/api/power_config.html).

We should modify the docstrings format of the inference modules to ensure the same output structure in the docs