feat: ibis_ml.metrics

[IndexSeek]

Explore adding a metrics module to support computing classification metrics such as accuracy, precision, recall, and f1_score, as well as regression metrics such as MSE, RMSE, MAE, and MAPE.

This was brought up in ibis-project/ibis#10501.

A challenge with this implementation, at least for classification, is that calculating these metrics individually may be less performant, as it likely requires reshaping the data first for each one. Even with this being the case, we would likely still get pretty good performance, and if the backend supports result caching, it would be even better in those instances.