[Feature] add `mlflow` metric_logging

[steveepreston]

Please add mlflow metric_logging. The lack of mlflow integration in torchtune is so painful.

[ebsmothers]

@steveepreston thanks for creating the issue. Based on this discussion seems like @fabiogeraci will take this on once he returns from leave

[fabiogeraci]

Back to work on the 8/01, I will start then

[steveepreston]

@ebsmothers Thanks for note @fabiogeraci Awesome!