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)

tests/fixtures/dataset_factories.py

@@ -474,9 +474,7 @@ def lerobot_dataset_metadata_factory(
         )
         with (
             patch("lerobot.common.datasets.lerobot_dataset.get_safe_version") as mock_get_safe_version_patch,
-            patch(
-                "lerobot.common.datasets.lerobot_dataset.snapshot_download"
-            ) as mock_snapshot_download_patch,
+            patch("lerobot.common.datasets.lerobot_dataset.snapshot_download") as mock_snapshot_download_patch,
         ):
             mock_get_safe_version_patch.side_effect = lambda repo_id, version: version
             mock_snapshot_download_patch.side_effect = mock_snapshot_download
@@ -558,9 +556,7 @@ def lerobot_dataset_factory(
         with (
             patch("lerobot.common.datasets.lerobot_dataset.LeRobotDatasetMetadata") as mock_metadata_patch,
             patch("lerobot.common.datasets.lerobot_dataset.get_safe_version") as mock_get_safe_version_patch,
-            patch(
-                "lerobot.common.datasets.lerobot_dataset.snapshot_download"
-            ) as mock_snapshot_download_patch,
+            patch("lerobot.common.datasets.lerobot_dataset.snapshot_download") as mock_snapshot_download_patch,
         ):
             mock_metadata_patch.return_value = mock_metadata
             mock_get_safe_version_patch.side_effect = lambda repo_id, version: version