Improve error reporting for few options in pg_createsubscriber

Hi,

Currently, error reports for database, publication, subscription, and
replication slots do not include the option name. This has been
addressed by including the option name in the error messages, ensuring
consistency similar to remove option. Additionally, pg_log_error and
exit(1) have been replaced with a single pg_fatal statement which
means the same. The attached patch implements these changes.

Regards,
Vignesh