Is your feature request related to a problem? Please describe.
I discovered this page (https://docs.bullmq.io/patterns/process-step-jobs#waiting-children) while looking for a solution to a problem I'm working on and thought the moveToWaitingChildren would be ideal for what I'm doing. I kept getting an error though saying job.moveToWaitingChildren is not a function and upon some digging discovered that the SandboxedJob interface does not define it and my worker is running a sandboxed processor.

Describe the solution you'd like
I'm not sure if there is a technical limitation for why sandboxed jobs can not implement the moveToWaitingChildren function but it would be nice if it was possible to use this function from within a sandboxed processor/job.

Describe alternatives you've considered
I noticed that the implementation of moveToWaitingChildren is pretty straightforward so I imported Scripts into my job and then tried

const scripts = new Scripts(queue);
scripts.moveToWaitingChildren(jobId, token)

But it just hangs for a minute and then I get a permanent failure on the job.