* use suffix of directory as group name and use directory as dbname
We can rename tpcds_sf1 to tpcds_sf1_p1, then tpcds_sf1 will be in group
p1. We will group cases to p0, p1, p2, p3 in the future.
p0: function cases running in seconds.
p1: cases with expected out running in minutes, like tpcds_sf1
p2: cases with expected out running in hours, like tpcds_sf10 tpcds_sf100
p3: cases without without expected out to test core dump.