[feature] WorkerPool with different configuration for queues

[ankush]

Right now we can provide fix list of queues for WorkerPool.

So if I have two queues but I want dedicated set of workers for one of the queue then I need to run a separate pool. This reduces benefit we can get from shared memory in pool.

Possible solution:

• Provide arguments for combination of queues+count.
• I am not sure what would be good CLI argument design for this

[ankush]

Potential CLI: rq worker-pool --queue x,y,z:5 --queue a,b,c:2

Internal structure can be dict[tuple[queue, ...], int]

[ankush]

@selwin will you accept a PR for something like this?