Run every operator both ways and report what it did

### Task Summary

The runner discovers the operators that implement the trait, configures each from its schema, runs it through the engine and through its generated script, and compares. An operator that cannot be run is reported as a row with the reason rather than passed over, since an operator missing from the report is a fact the report has to carry.

`OperatorBehaviorSpec` is what turns that into tests: one per operator per configuration its schema offers, named so a single operator can be run alone.

Step 23 of 27 in #8325. It reads the generator trait, so it needs #8327, and its assertions name operators the family steps carry, so it comes after them rather than before.