[SPARK-16469] enhanced simulate multiply

## What changes were proposed in this pull request?

We have a use case of multiplying very big sparse matrices. we have about 1000x1000 distributed block matrices multiplication and the simulate multiply goes like O(n^4) (n being 1000). it takes about 1.5 hours. We modified it slightly with classical hashmap and now run in about 30 seconds O(n^2).

## How was this patch tested?

We have added a performance test and verified the reduced time.

Author: oraviv <oraviv@paypal.com>

Closes #14068 from uzadude/master.