add get_custom_data_collator feature

recipes/quickstart/finetuning/datasets/vqa_dataset.py

recipes/quickstart/finetuning/datasets/vqa_dataset_old.py

src/llama_recipes/datasets/__init__.py

src/llama_recipes/datasets/custom_dataset.py

src/llama_recipes/finetuning.py

src/llama_recipes/utils/config_utils.py

src/llama_recipes/utils/dataset_utils.py