SqlPgsql::dbExists checking exit code is not enough

[Sweetchuck]

Problem

\Drush\Sql\SqlPgsql::dbExists()
Always returns TRUE with PostgreSQL-15.

Exit code of the command psql --no-psqlrc -t -c "SELECT 1 AS result FROM pg_database WHERE datname='foo'" shows that the query ran successfully.
It doesn't care about the number of records.

When the database IS exists, then the stdOutput is 1\n\n
When the database IS NOT exists, then the stdOutput is \n. It is not an empty string, so it is converted to TRUE.

Suggested solution

return $process->isSuccessful()
    && trim($process->getOutput()) === '1';

Originally posted by @Sweetchuck in #5545 (comment)