Add weight/priority to queue groups

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Proposal

When working with a customer for routing rules we noticed that their rails node would pick up jobs before their sidekiq nodes. They have a specific rule for their rails nodes but this still includes roughly 500 queues.

## Routing rules
sidekiq['routing_rules'] = [
  ['feature_category!=global_search,container_registry,value_stream_management,code_testing&resource_boundary!=cpu&urgency=high', 'rails-node'],
  ['*', 'default']
]

This results in their Sidekiq nodes doing almost nothing while their Rails nodes handle the most jobs.

My proposal is adding a weight/priority for queue groups to regulate where the jobs are going more clearly.

## Rails
sidekiq['queue_groups'] = [
 'rails-node&priority=2',
 'rails-node&priority=2'
]

## Sidekiq
sidekiq['queue_groups'] = [
 'rails-node&priority=1',
 'rails-node&priority=1',
 'default',
 'default,mailers'
] 

This would prioritize the Sidekiq nodes over the Rails nodes using the Rails node as a backup.

Ticket https://gitlab.zendesk.com/agent/tickets/531724 (internal only)