Add WrapperConfig for environment wrappers and update SACConfig properties

- Introduced `WrapperConfig` dataclass for environment wrapper configurations.
- Updated `ManiskillEnvConfig` to include a `wrapper` field for enhanced environment management.
- Modified `SACConfig` to return `None` for `observation_delta_indices` and `action_delta_indices` properties.
- Refactored `make_robot_env` function to improve readability and maintainability.

lerobot/common/policies/sac/configuration_sac.py

@@ -233,11 +233,11 @@ class SACConfig(PreTrainedConfig):
 
     @property
     def observation_delta_indices(self) -> list:
-        return list(range(1 - self.n_obs_steps, 1))
+        return None
 
     @property
     def action_delta_indices(self) -> list:
-        return [0]  # SAC typically predicts one action at a time
+        return None  # SAC typically predicts one action at a time
 
     @property
     def reward_delta_indices(self) -> None: