[Feature]: TensorDictPrimer transform

[nicolas-dufour]

Description

This PR add a ForceTensorReset transform.

Motivation and Context

ForceTensorReset allows to set or reset to default values some given vectors

Types of changes

What types of changes does your code introduce? Remove all that do not apply:

• New feature (non-breaking change which adds core functionality)

Checklist

Go over all the following points, and put an x in all the boxes that apply.
If you are unsure about any of these, don't hesitate to ask. We are here to help!

• I have read the CONTRIBUTION guide (required)
• My change requires a change to the documentation.
• I have updated the tests accordingly (required for a bug fix or a new feature).
• I have updated the documentation accordingly.

[vmoens]

Lint!

[vmoens]

ForceTensorReset is not very indicative IMO
What about

• DefaultTensorRest
• DefaultValueReset
• TensorDictPrimerReset
• TensorDictPrimer
• TensorDictPrimerTransform

[vmoens]

Added TensorDictPrimer
Let me know if that's a suitable solution. The big advantage is that the spec is registered in the env, and we can execute rollouts in parallel without problem as the tensordict will be properly pre-allocated.
If you're fine with it, can you remove ForceTensorReset as well as the tests?
You can rename the class if you feel like it :)

[nicolas-dufour]

The transform is still needed to properly reset the states. Thank you for the changes to rollout!. I'll rename it to DefaultTensorReset if that's ok with you

[vmoens]

Have you looked at my solution? It does reset things. What does ForceTensorReset do that TensorDictPrimer does not?

[nicolas-dufour]

I'm not sure i understand how i can set vectors that aren't given by the env with TensorDictPrimer. Like prior_state and belief

[vmoens]

Look at the docstring :)

[nicolas-dufour]

Ah it's with the kwargs. Ok i will remove my tests and transform then