Fix call to Intersect() in TestLeafNodeIntersections()

[Tyler799]

The call here is different (I suspect old) in which the first two parameters are a min_t and max_t instead of local_t, so the call is invalid. Not sure what else needs to change.

If TestLeafNodeIntersections() itself is deprecated it should be removed or replaced.

[syoyo]

TestLeafNodeIntersections is used in NanoSG example(for two-level BVH traverse) and NanoSG supplies custom Intersector class for it https://github.com/lighttransport/nanort/blob/master/examples/nanosg/nanosg.h#L571

We may better to assign different class(template) name for TestLeafNodeIntersections to distinguish Intersector used in Traverse