speeding up caches for hfsort+

Summary:
When running hfsort+, we invalidate too many cache entries, which leads to inefficiencies. It seems we only need to invalidate cache for pairs of clusters (Into, X) and (X, Into) when modifying cluster Into (for all clusters X).
With the modification, we do not really need ShortCache, since it is computed only once per pair of clusters.

(cherry picked from FBD6341039)