[Feature] Call Worker and QueueScheduler methods without launching the process

Manually processing jobs like this: https://docs.bullmq.io/patterns/manually-fetching-jobs can cause problems because new Worker launches the process instantly. This can cause a lot of unpredictable effects in support scripts if I just want to manually resolve issues in a queue without processing any single job from there.

Is it possible to add a constructor option to prevent the process from being launched instantly. Like:

const worker = new Worker(name, () => {}, {autorun: false})

Overall, I think calling run() in constructor is an anti-pattern: you don’t make all the methods of Worker class easily accessible this way.

[manast]

@bogdan regarding my comment above. Although technically you do not need to duplicate the connection, in practice whatever connection you use will be blocked as soon as you call getNextJob. So I think the duplication makes sense to be performed always to avoid weirs issues where the user expects something to happen but nothing happens because the connection is blocked.

[bogdan]

@roggervalf looks good! Can you also add methods I mentioned in https://github.com/taskforcesh/bullmq/issues/436#issuecomment-804891421 or can I open another issue to add them?