fix(tests)

- Updated `lerobot_dataset.py:add_frame` to take task as key in frame
- Updated `lerobot_dataset.py` to remove robot argument from `create` function of lerobotdataset and lerobotdatasetmetadata and directly take the features
- Update `test_datasets.py` to features from Mock robot
- Update all the usage of `add_frame` in the library
- Update `dataset_factories.py`; had issues with new argument order
- Raise ValueError when no task is provided (in `datasets/utils.py` validate func)

lerobot/common/utils/buffer.py

@@ -596,7 +596,8 @@ class ReplayBuffer:
                         frame_dict[f"complementary_info.{key}"] = val
 
             # Add to the dataset's buffer
-            lerobot_dataset.add_frame(frame_dict, task=task_name)
+            frame_dict["task"] = task_name
+            lerobot_dataset.add_frame(frame_dict)
 
             # Move to next frame
             frame_idx_in_episode += 1