[common] (datasets) refactor zoo: drop the enum usage for a custom metaclass

common/research/common/dataset/directory_roco_dataset.py

common/research/common/dataset/dji/__init__.py

common/research/common/dataset/dji/dji_roco_datasets.py

...n/research/common/dataset/dji/dji_roco_zoomed_datasets.py

common/research/common/dataset/roco_dataset.py

common/research/common/dataset/split.py

common/research/common/dataset/tensorflow_record.py

...on/research/common/dataset/twitch/twitch_roco_datasets.py

common/research/common/dataset/union_dataset.py

common/research/common/datasets_v3/dataset_builder.py

...search/common/datasets_v3/roco/roco_dataset_descriptor.py

common/research/common/datasets_v3/roco/roco_datasets.py

common/research/common/datasets_v3/roco/zoo/dji.py

common/research/common/datasets_v3/roco/zoo/dji_zoomed.py

common/research/common/datasets_v3/roco/zoo/twitch.py

common/research/common/scripts/create_tensorflow_records.py

common/research/common/scripts/improve_roco_by_zooming.py

common/research/common/scripts/visualize_dataset.py

...earch/robots_at_robots/armor_color/armor_color_dataset.py

...arch/robots_at_robots/armor_color/baseline_experiments.py