message: Properly return constant vector from timestamp functions as well
diff: @@ -13,24 +13,21 @@ static void current_time_function(DataChunk &input, ExpressionState &state, Vect
  assert(input.column_count == 0);
  auto val = Value::INTEGER(Timestamp::GetTime(Timestamp::GetCurrentTimestamp()));
  - result.count = 1;
  - result.SetValue(0, val);
  + result.Reference(val);
  }
  static void current_date_function(DataChunk &input, ExpressionState &state, Vector &result) {
  assert(input.column_count == 0);
  auto val = Value::INTEGER(Timestamp::GetDate(Timestamp::GetCurrentTimestamp()));
  - result.count = 1;
  - result.SetValue(0, val);
  + result.Reference(val);
  }
  static void current_timestamp_function(DataChunk &input, ExpressionState &state, Vector &result) {
  assert(input.column_count == 0);
  auto val = Value::TIMESTAMP(Timestamp::GetCurrentTimestamp());
  - result.count = 1;
  - result.SetValue(0, val);
  + result.Reference(val);
  }
  void CurrentTimeFun::RegisterFunction(BuiltinFunctions &set) {
  