Add a public utility function get grad scaler(distributed type=None, kwargs) in accelerate/utils/modeling.py…

Add a public utility function get grad scaler(distributed type=None, kwargs) in accelerate/utils/modeling.py…: a task in HF ML Tasksmith (Harbor dataset). All kwargs (e.g. init scale , growth factor , backoff factor , growth interval , enabled ) are forwarded to the chosen constructor.