refactor(processor): improve processor pipeline typing with generic type (#1810)

* refactor(processor): introduce generic type for to_output

- Always return `TOutput`
- Remove `_prepare_transition`, so `__call__` now always returns `TOutput`
- Update tests accordingly
- This refactor paves the way for adding settings for `to_transition` and `to_output` in `make_processor` and the post-processor

* refactor(processor): consolidate ProcessorKwargs usage across policies

- Removed the ProcessorTypes module and integrated ProcessorKwargs directly into the processor pipeline.
- Updated multiple policy files to utilize the new ProcessorKwargs structure for preprocessor and postprocessor arguments.
- Simplified the handling of processor kwargs by initializing them to empty dictionaries when not provided.

tests/processor/test_rename_processor.py

@@ -188,7 +188,7 @@ def test_integration_with_robot_processor():
     }
     rename_processor = RenameProcessor(rename_map=rename_map)
 
-    pipeline = RobotProcessor([rename_processor])
+    pipeline = RobotProcessor([rename_processor], to_transition=lambda x: x, to_output=lambda x: x)
 
     observation = {
         "agent_pos": np.array([1.0, 2.0, 3.0]),
@@ -236,7 +236,9 @@ def test_save_and_load_pretrained():
         assert len(state_files) == 0
 
         # Load pipeline
-        loaded_pipeline = RobotProcessor.from_pretrained(tmp_dir)
+        loaded_pipeline = RobotProcessor.from_pretrained(
+            tmp_dir, to_transition=lambda x: x, to_output=lambda x: x
+        )
 
         assert loaded_pipeline.name == "TestRenameProcessor"
         assert len(loaded_pipeline) == 1
@@ -277,7 +279,7 @@ def test_registry_functionality():
 def test_registry_based_save_load():
     """Test save/load using registry name instead of module path."""
     processor = RenameProcessor(rename_map={"key1": "renamed_key1"})
-    pipeline = RobotProcessor([processor])
+    pipeline = RobotProcessor([processor], to_transition=lambda x: x, to_output=lambda x: x)
 
     with tempfile.TemporaryDirectory() as tmp_dir:
         # Save and load
@@ -318,7 +320,7 @@ def test_chained_rename_processors():
         }
     )
 
-    pipeline = RobotProcessor([processor1, processor2])
+    pipeline = RobotProcessor([processor1, processor2], to_transition=lambda x: x, to_output=lambda x: x)
 
     observation = {
         "pos": np.array([1.0, 2.0]),