message: Enable simple parallelism for hash group by (with global lock on HT)
diff: #include "duckdb/execution/operator/aggregate/physical_simple_aggregate.hpp"
  #include "duckdb/execution/operator/scan/physical_table_scan.hpp"
  +#include "duckdb/execution/operator/aggregate/physical_hash_aggregate.hpp"
  using namespace std;
  @@ -145,6 +146,13 @@ void Pipeline::Schedule() {
  }
  break;
  }
  + case PhysicalOperatorType::HASH_GROUP_BY: {
  + if (ScheduleOperator(sink->children[0].get())) {
  + // all parallel tasks have been scheduled: return
  + return;
  + }
  + break;
  + }
  default:
  break;
  }
  