Feature Request: RecurringJobs more Random Times

Currently we have a Job that should run on Random Times roughly every 3 hours.
It would be good idea, to actually make that happen with Hangfire.

Actually if "true" async Background Tasks would be supported, one could actually use `Task.Delay` to further Delay the execution, however as it is implemented, a Task.Delay would hold on the Thread instead of putting it back to the thread pool and do the next task

No files, tests, or entry points are named. Start by tracing recurring-job scheduling and background task execution, then define how roughly three-hour random delays should be represented without holding a worker thread; done means the behavior is specified and covered by tests.

Written by the indexing model from the issue text.