Feature/dv3 parallel stochastic

[belerico]

Summary

This PR introduces the possiblity to have the Dreamer-V3 representation model (the one responsible to output the posterior) to be independent from the recurrent model.

Type of Change

Please select the one relevant option below:

• New feature (non-breaking change that adds functionality)

Checklist

Please confirm that the following tasks have been completed:

• I have tested my changes locally and they work as expected. (Please describe the tests you performed.)
• I have added unit tests for my changes, or updated existing tests if necessary.
• I have updated the documentation, if applicable.
• I have installed pre-commit and run locally for my code changes.

Screenshots or Visuals (Optional)

where the pink one is DV3 with the parallel stochastic while the blue is the standard one.

Additional Information (Optional)

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• Any potential risks or challenges associated with the changes.
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