Move RL off TF / tf_agents

[mtrofin]

We'd still use saved models / tflite as serialization format and means to pass models to the compiler.

Another possibility is moving to pytorch, if we can get from pytorch to saved models / tflite.

[petrhosek]

If we decide to move to JAX, we should use Orbax Model (OBM) as the alternative for TensorFlow SavedModel.

[Harishankar14]

@petrhosek Thanks for the suggestion + link to the repo.