Allow pgbench to exit immediately when any client is aborted.

Allow pgbench to exit immediately when any client is aborted.

Previously when client was aborted due to some error during
benchmarking, other clients continued their run until certain number
of transactions specified -t was reached or the time specified by -T
was expired. At the end, the results are printed with caution: "Run
was aborted; the above results are incomplete" shows.

New option "--exit-on-abort" allows pgbench to exit immediately in
this case so that users could quickly fix the cause of the failure and
try again another round of benchmarking.

Author: Yugo Nagata
Reviewed-by: Fabien COELHO, Tatsuo Ishii
Discussion: https://postgr.es/m/flat/20230804130325.df32e60879c38c92bca64207%40sraoss.co.jp