Add means to initialize queue group cache for existing queues

Queue-specific options can be specified for each queue in the queue group as of EVG-15931. However, these only apply to newly-created queues, not queues that already exist in the DB. For those, they're populated in the cache when the queue group is first constructed and maintained by the background create goroutine. There should be a mechanismto ensure that existing queues can be initialized with queue-specific options when the queue group is first constructed and the cache is populated.