Support onData(..) prop to also receive # of aggregation terms

**Issue Type:**

Enhancement / Idea

**Description:**

Add a extra arg in the `onData(..)` method of components that either perform aggregation or receive hits for `resultStats`.

This can enable the user to customize component's display behavior: For instance, if results found are below a threshold - hide the component from the view, or decide to not update the previous component's view and make the values un-selectable.