Add a new ActionType::SOURCE_SET for handling the case where we inspect the source sets of the origin. This requires the addition of two new fields to Action as well that are only used with this action type. Hence the unions.

Add a new ActionType::SOURCE_SET for handling the case where we inspect the source sets of the origin. This requires the addition of two new fields to Action as well that are only used with this action type. Hence the unions. #2831