refactor(processor): clarify action types, distinguish PolicyAction, RobotAction, and EnvAction (#1908)

* refactor(processor): split action from policy, robots and environment

- Updated function names to robot_action_to_transition and robot_transition_to_action across multiple files to better reflect their purpose in processing robot actions.
- Adjusted references in the RobotProcessorPipeline and related components to ensure compatibility with the new naming convention.
- Enhanced type annotations for action parameters to improve code readability and maintainability.

* refactor(converters): rename robot_transition_to_action to transition_to_robot_action

- Updated function names across multiple files to improve clarity and consistency in processing robot actions.
- Adjusted references in RobotProcessorPipeline and related components to align with the new naming convention.
- Simplified action handling in the AddBatchDimensionProcessorStep by removing unnecessary checks for action presence.

* refactor(converters): update references to transition_to_robot_action

- Renamed all instances of robot_transition_to_action to transition_to_robot_action across multiple files for consistency and clarity in the processing of robot actions.
- Adjusted the RobotProcessorPipeline configurations to reflect the new naming convention, enhancing code readability.

* refactor(processor): update Torch2NumpyActionProcessorStep to extend ActionProcessorStep

- Changed the base class of Torch2NumpyActionProcessorStep from PolicyActionProcessorStep to ActionProcessorStep, aligning it with the current architecture of action processing.
- This modification enhances the clarity of the class's role in the processing pipeline.

* fix(processor): main action processor can take also EnvAction

---------

Co-authored-by: Steven Palma <steven.palma@huggingface.co>

src/lerobot/processor/__init__.py

@@ -46,11 +46,13 @@ from .pipeline import (
     IdentityProcessorStep,
     InfoProcessorStep,
     ObservationProcessorStep,
+    PolicyActionProcessorStep,
     PolicyProcessorPipeline,
     ProcessorKwargs,
     ProcessorStep,
     ProcessorStepRegistry,
     RewardProcessorStep,
+    RobotActionProcessorStep,
     RobotProcessorPipeline,
     TruncatedProcessorStep,
 )
@@ -81,10 +83,12 @@ __all__ = [
     "NormalizerProcessorStep",
     "Numpy2TorchActionProcessorStep",
     "ObservationProcessorStep",
+    "PolicyActionProcessorStep",
     "PolicyProcessorPipeline",
     "ProcessorKwargs",
     "ProcessorStep",
     "ProcessorStepRegistry",
+    "RobotActionProcessorStep",
     "RenameObservationsProcessorStep",
     "RewardClassifierProcessorStep",
     "RewardProcessorStep",