stats_cartesian_product computes incorrect byte size for cross join #22699

Describe the bug

      // the result size is two times a*b because you have the columns of both left and right
      let total_byte_size = left_stats
          .total_byte_size
          .multiply(&right_stats.total_byte_size)
          .multiply(&Precision::Exact(2));

This formula is wrong: we're multiplying two byte-size values together, which doesn't make sense. The right formula is (left_rows * right_row_count) + (right_rows * left_row_count).

To Reproduce

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Expected behavior

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Additional context

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