pgbench: Use common logging API

Author: Fabien COELHO <coelho@cri.ensmp.fr>
Reviewed-by: Michael Paquier <michael@paquier.xyz>
Reviewed-by: Peter Eisentraut <peter.eisentraut@2ndquadrant.com>
Discussion: https://www.postgresql.org/message-id/flat/alpine.DEB.2.21.1912241100390.3339@pseudo

Author: petere