text: Title: [Bug]: MODEL_ZOO is not reused in subprocesses
  Body: Since `model_key` (the hash of partial function) changes in mapped processes, the preloaded models are never truly reused.
  
  https://github.com/modelscope/data-juicer/blob/aaa404a5b12c9ef87ebf54a7bf38c7b4bcbfd0f1/data_juicer/utils/model_utils.py#L546-L549