Improve handling of jobs

[jonasraoni]

Extracted from #9822

• Ensure jobs can be terminated gracefully (store the progress somewhere), and be careful with things that shouldn't be executed twice (e.g. sending an email)
• The BaseJob have some default values (default timeout of 60s, backoff of 5s, etc), I think it's better to make it required instead of providing random default values. Forcing the programmer to fill in these values, it's also a good reminder to treat the exceptional cases.
• It's difficult to estimate how long some jobs might run (e.g. a large installation might require much more time). So, I think the timeout should be removed (or have a really high value), if it's not possible to update the code to terminate gracefully (i.e. resume the work from where it stopped later).
• Looks like the Laravel doesn't have a isTimedOut() method, we could add it and update the code to respect it (e.g. while (!$this->isTimedOut()) { doWork(); }) instead of using the $failOnTimeout = true, it sounds better for most of the cases. IMHO abruptly timeouts are good only to catch bad code (e.g. infinite loops)...