Remove HiveRelBuilder.aggregateCall override and refactor callers to use existing public methods

The HiveRelBuilder overrides aggregateCall from its superclass simply to expose and use it in HiveRewriteToDataSketchesRules.

However, there is no real need to override this method since we can achieve the same outcome by using existing methods in RelBuilder which are easier to use and understand. Furthermore it is safer to depend on public APIs since are more stable in general.