pgbench: Add --continue-on-error option.

pgbench: Add --continue-on-error option.

This commit adds the --continue-on-error option, allowing pgbench clients
to continue running even when SQL statements fail for reasons other than
serialization or deadlock errors. Without this option (by default),
the clients aborts in such cases, which was the only available behavior
previously.

This option is useful for benchmarks using custom scripts that may
raise errors, such as unique constraint violations, where users want
pgbench to complete the run despite individual statement failures.

Author: Rintaro Ikeda <ikedarintarof@oss.nttdata.com>
Co-authored-by: Yugo Nagata <nagata@sraoss.co.jp>
Co-authored-by: Fujii Masao <masao.fujii@gmail.com>
Reviewed-by: Stepan Neretin <slpmcf@gmail.com>
Reviewed-by: Matthias van de Meent <boekewurm+postgres@gmail.com>
Reviewed-by: Dilip Kumar <dilipbalaut@gmail.com>
Reviewed-by: Srinath Reddy Sadipiralla <srinath2133@gmail.com>
Reviewed-by: Hayato Kuroda <kuroda.hayato@fujitsu.com>
Reviewed-by: Anthonin Bonnefoy <anthonin.bonnefoy@datadoghq.com>
Reviewed-by: Chao Li <lic@highgo.com>
Discussion: https://postgr.es/m/44334231a4d214fac382a69cceb7d9fc@oss.nttdata.com