drush/wp-cli/cv - make behaviour more UNIX-y

Currently, commands like Drush when executing cron generate output to stdout for each run.

drush civicrm-api -u 1 job.execute
drush @example.org -u civicrm.cron job.execute
drush -r /var/www/example.org -l https://example.org civicrm-api -u civicrm.cron job.execute

This "doesn't feel UNIX-y" to me, as I expect a successful job to make no output (unless the purpose of the CLI tool is to generate output). (Rationale: "Rule of Silence", from ESR's "17 Unix Rules".)

It would be good to have drush/wp-cli/cv deliver meaningful exit codes and have a means of operation which makes them silent on success.

Background discussion:

• https://chat.civicrm.org/civicrm/pl/t4z84irhcjfb3bw5gkcg9x1ddw
• https://chat.civicrm.org/civicrm/pl/3u89pm3gdig58jbbsojdn8tokc
• https://chat.civicrm.org/civicrm/pl/j87dsqbcatgmuqzczs9915471h