refactor(pi0): rename PI0OpenPIConfig and PI0OpenPIPolicy to PI0Config and PI0Policy

- Updated imports and references throughout the codebase to reflect the new naming convention.
- Introduced a new processor file for PI0 to handle pre-processing and post-processing steps.
- Adjusted tests to utilize the renamed classes, ensuring consistency and functionality.
- Enhanced clarity and maintainability by removing outdated naming conventions.

tests/policies/pi0_pi05/test_pi0_openpi.py

@@ -14,10 +14,10 @@ pytestmark = pytest.mark.skipif(
 )
 
 from lerobot.policies.factory import make_policy_config  # noqa: E402
-from lerobot.policies.pi0_openpi import (  # noqa: E402
-    PI0OpenPIConfig,
-    PI0OpenPIPolicy,
-    make_pi0_openpi_pre_post_processors,  # noqa: E402
+from lerobot.policies.pi0 import (  # noqa: E402
+    PI0Config,
+    PI0Policy,
+    make_pi0_pre_post_processors,  # noqa: E402
 )
 from lerobot.utils.random_utils import set_seed  # noqa: E402
 from tests.utils import require_cuda  # noqa: E402
@@ -30,7 +30,7 @@ def test_policy_instantiation():
     # Create config
 
     set_seed(42)
-    config = PI0OpenPIConfig(max_action_dim=7, max_state_dim=14, dtype="float32")
+    config = PI0Config(max_action_dim=7, max_state_dim=14, dtype="float32")
 
     # Set up input_features and output_features in the config
     from lerobot.configs.types import FeatureType, PolicyFeature
@@ -70,10 +70,8 @@ def test_policy_instantiation():
     }
 
     # Instantiate policy
-    policy = PI0OpenPIPolicy(config)
-    preprocessor, postprocessor = make_pi0_openpi_pre_post_processors(
-        config=config, dataset_stats=dataset_stats
-    )
+    policy = PI0Policy(config)
+    preprocessor, postprocessor = make_pi0_pre_post_processors(config=config, dataset_stats=dataset_stats)
     # Test forward pass with dummy data
     batch_size = 1
     device = config.device