Integrate `AdversarialTextGenerationPipeline` into `-m llmart` flow

[dxoigmn]

Right now we have two distinct flows:

1. A command-line interface via -m llmart that we use when scaling experiments.
2. A code-based interface using AdversarialTextGenerationPipeline that we use in examples.

We should to integrate AdversarialTextGenerationPipeline into the main command-line interface.