FR: Add a per-schedule option to disable logging runs

With a new feature allowing to schedule jobs with second granularity, `job_run_details` is clogged very-very fast rendering it practically useless, especially if you do want to keep log run details for your critical jobs and discard them for routine queries.

Adding an argument to disable logging per-schedule would be very helpful:

```
cron.schedule(job_name text, schedule text, command text, log boolean)
```