Add HuggingFaceCheckpointer option for only registering final checkpoint

[irenedea]

This would allow us to avoid saving an extra final checkpoint at the end of training.

Example Usage

  hf_checkpointer:
    precision: bfloat16
    save_folder: ./local_checkpoints
    save_interval: 1h
    mlflow_logging_config:
      task: llm/v1/chat
      metadata:
        task: llm/v1/chat
        pretrained_model_name: meta-llama/Meta-Llama-3-8B
        databricks_model_family: LlamaForCausalLM (llama-3)
        databricks_model_source: genai-fine-tuning
        databricks_model_size_parameters: 8b
    mlflow_registered_model_name: ift-meta-llama-3-8b-ohuja8
    final_register_only: true

Branch for testing: final-register-only-fallback This adds irenedea@f63b5e0 which raises an error.

fallback: test-final-register-only-fallback-ATwQG5
normal: test-final-register-only-SKerij

[KuuCi]

lgtm aside from that one snipbit I don't quite understand.

[snarayan21]

seems chill to me, would like @dakinggg to take a pass

[dakinggg]

one typo i think, otherwise lgtm