[12.x] Add default scheduler output

[thierry2015]

What

Allow setting the default output for scheduled work directly in the schedule instance

Why

Despite having the option at a few levels, including the scheduled event itself (e.g., $schedule->command('inspire')->appendOutputTo('/dev/stdout'), the schedule:work command, to name a few, there is, as far as I know, no centralized output configuration for the scheduler. It can be beneficial for those running the scheduler in ephemeral and/or container-driven ecosystems (e.g., Kubernetes jobs), or in a space where the filesystem may not be the most suitable log storage system, to better control where the scheduler's output should be written.

This answers a few questions/threads/requests:

• Scheduled Tasks should be able to output to STDOUT - currently forced to /dev/null or file #47448
• https://laracasts.com/discuss/channels/laravel/output-from-scheduler-to-stdout