refactor(dataset): split LeRobotDataset into DatasetReader & DatasetWriter (+ API cleanup) (#3180)

* refactor(dataset): split reader and writer

* chore(dataset): remove proxys

* refactor(dataset): better reader & writer encapsulation

* refactor(datasets): clean API + reduce leaky implementations

* refactor(dataset): API cleaning for writer, reader and meta

* refactor(dataset): expose writer & reader + other minor improvements

* refactor(dataset): improve teardown routine

* refactor(dataset): add hf_dataset property at the facade level

* chore(dataset): add init for datasset module

* docs(dataset): add docstrings for public API of the dataset classes

* tests(dataset): add tests for new classes

* fix(dataset): remove circular dependecy

examples/lekiwi/replay.py

@@ -35,9 +35,7 @@ def main():
 
     # Fetch the dataset to replay
     dataset = LeRobotDataset("<hf_username>/<dataset_repo_id>", episodes=[EPISODE_IDX])
-    # Filter dataset to only include frames from the specified episode since episodes are chunked in dataset V3.0
-    episode_frames = dataset.hf_dataset.filter(lambda x: x["episode_index"] == EPISODE_IDX)
-    actions = episode_frames.select_columns(ACTION)
+    actions = dataset.select_columns(ACTION)
 
     # Connect to the robot
     robot.connect()
@@ -48,7 +46,7 @@ def main():
 
         print("Starting replay loop...")
         log_say(f"Replaying episode {EPISODE_IDX}")
-        for idx in range(len(episode_frames)):
+        for idx in range(dataset.num_frames):
             t0 = time.perf_counter()
 
             # Get recorded action from dataset