cuboid sharding based on specific column

currently cuboid sharding is based on the hash value of the row key. If we allow computing hash value on a specific column C, then we're actually partitioning the data w.r.t C. The benefit is that if we later a query with filter like "where C = 'xyz'", kylin can skip shards. Also for filter like "where C IN

", kylin can prune candidates sent to different shards