HLL_HASH function return type should be HLL #3652
Description
Currently, the return value of the HLL function is varchar. This result in problems in analyze stage. For example, HLL_RAW_AGG(hll_hash(hll_type_field)) return analyze error: "HLL_UNION_AGG, HLL_RAW_AGG and HLL_CARDINALITY's params must be HLL column".