High impact pair entity ID requires a scan of dataset

# 🙋 feature request

Currently, using the high impact pair records requires that the client find, fetch, and scan the entire dataset for each of the records referenced by the high impact pair.

More friendly options would be:

- (Best) Have the pair information populated directly into the results of `high_impact_pairs().records()`
- (Good) Be able to fetch a single record by `tamr_id` from a dataset.

## 🔦 Context

`high_impact_pairs` is far less performant / scale-conscious in the API than it is in the UI. The UI shows high impact pairs efficiently, which the API requires a full scan of the source datasets.