Vectorization: Scale up small hashtables, when collisions are detected

Hive's hashtable estimates are getting better with HyperLogLog stats in place, but an accurate estimate does not always result in a low number of collisions.

The hashtables which contain a very small number of items tend to lose their O(1) lookup performance where there are collisions. Since collisions are easy to detect within the fast hashtable implementation, a rehashing to a higher size will help these small hashtables avoid collisions and go back to O(1) perf.