Standardize metric ranges

Several common metrics, like `exact_match` and `f1`, sometimes range from 0-1, and sometimes from 0-100.

As discussed with @lhoestq , we think it makes more sense to report them from 0-1, which would entail changing the code of metrics such as [CUAD](https://github.com/huggingface/datasets/blob/master/metrics/cuad/cuad.py).

@emibaylor and I will add other metrics here that we see reporting scores from 0-100 instead of 0-1.