Add explainers for cost-benefit analysis

[zyteka]

A common need in decision-making is to understand not just what a model says the right decision is, but to understand the expected cost and benefits of a decision. Given pyreal's use case, it may be worth it to consider explainers that include this kind of cost-benefit analysis. This will likely require such explainers to take additional data.

Completing this issue will involve writing up one or more issues with more hashed out details as to what this would look like.