🧪 [Experimental] Train LeRobot policy with TRL

[qgallouedec]

What does this PR do?

This PR is the support for experimental work to use trl to train the policies of LeRobot.

Before submitting

• This PR fixes a typo or improves the docs (you can dismiss the other checks if that's the case).
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• Did you write any new necessary tests?

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