* Add "Rows out" print in cdbexplain_showExecStats

set gp_enable_explain_rows_out=on;

explain (analyze,verbose,format text) select * from tt where a > b;

                                                          QUERY PLAN
-------------------------------------------------------------------------------------------------------------------------------
 Gather Motion 3:1  (slice1; segments: 3)  (cost=0.00..431.00 rows=1 width=8) (actual time=2.534..223.679 rows=499500 loops=1)
   Output: a, b
   ->  Seq Scan on public.tt  (cost=0.00..431.00 rows=1 width=8) (actual time=0.145..127.350 rows=166742 loops=1)
         Output: a, b
         Filter: (tt.a > tt.b)
         Rows out: 166500.00 rows avg x 3 workers, 166742 rows max (seg0), 166340 rows min (seg2).
...