Support automatic selection of queues (Enhancement)

It would be nice if instead of static list in BackgroundServerOptions for Queues we had a Func ProcessQueues, that is based on existing queues. That would allow processing for dynamic queues.

For example, we have a multi-tenancy application where each tenant has a separate queue and we would like to have an ability to scale processing per tenant.
`
var backgroundServerOptions = new BackgroundServerOptions() {
ProcessQueues = s => s.StartsWith("tenantcode") or s => config.Tenants.Contains(s) etc.
};
`

Start with BackgroundServerOptions and trace how the static Queues setting is used to select queues for processing. Define the behavior for a predicate based on existing queues, including how queue discovery and processing scale per tenant; the issue is complete when dynamic queue selection works without requiring a static list.

Written by the indexing model from the issue text.