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/device_processor.py

@@ -27,7 +27,7 @@ import torch
 from lerobot.configs.types import PipelineFeatureType, PolicyFeature
 from lerobot.utils.utils import get_safe_torch_device
 
-from .core import EnvTransition, TransitionKey
+from .core import EnvTransition, PolicyAction, TransitionKey
 from .pipeline import ProcessorStep, ProcessorStepRegistry
 
 
@@ -129,6 +129,10 @@ class DeviceProcessorStep(ProcessorStep):
             A new `EnvTransition` object with all tensors moved to the target device and dtype.
         """
         new_transition = transition.copy()
+        action = new_transition.get(TransitionKey.ACTION)
+
+        if action is not None and not isinstance(action, PolicyAction):
+            raise ValueError(f"If action is not None should be a PolicyAction type got {type(action)}")
 
         simple_tensor_keys = [
             TransitionKey.ACTION,