feat(processors): Add ToBatchProcessor to multiple policy processors

- Integrated ToBatchProcessor into various policy processors to handle observation batching.
- Updated make functions for act, diffusion, pi0, pi0fast, sac, smolvla, tdmpc, and vqbet processors to include the new batching functionality.
- Ensured consistency across all processor implementations for improved data handling.

src/lerobot/policies/diffusion/processor_diffusion.py

@@ -20,6 +20,7 @@ from lerobot.policies.diffusion.configuration_diffusion import DiffusionConfig
 from lerobot.processor import (
     NormalizerProcessor,
     RobotProcessor,
+    ToBatchProcessor,
     UnnormalizerProcessor,
 )
 
@@ -34,6 +35,7 @@ def make_diffusion_processor(
         NormalizerProcessor(
             features=config.output_features, norm_map=config.normalization_mapping, stats=dataset_stats
         ),
+        ToBatchProcessor(),
     ]
     output_steps = [
         UnnormalizerProcessor(