- tf: TensorFlow 2/Sonnet 2/TRFL-based agents.
- jax: JAX/Haiku/rlax-based agents.
- third_party: Agents created by third parties (not DeepMind).

Also adopt more standard naming practice within each agent folder (agent.py).

PiperOrigin-RevId: 305674544
Change-Id: I3d4f076fb96d2e0250cfbb3f1adf163ce6932e97