Consider a failed process as a failed test in pg_regress

Consider a failed process as a failed test in pg_regress

Commit 55de145d1cf added reporting of child process failures, but the
test suite is still allowed to pass even if the process failed. Since
regress tests are higher level tests, a false positive is more likely
in this case so report failed test processes as failed tests.

Reported-by: Andres Freund <andres@anarazel.de>
Discussion: https://postgr.es/m/82C46B5E-1821-4039-82C2-56BCA5992989@yesql.se
Discussion: https://postgr.es/m/20221122235636.4frx7hjterq6bmls@awork3.anarazel.de