[fix][broker] Send ActiveConsumerChange for non-persistent Failover subscriptions

[Dream95]

Fixes #23491

Main Issue: #xyz

PIP: #xyz

Motivation

Non-persistent Failover subscriptions did not send ActiveConsumerChange when the active consumer changed. PersistentDispatcherSingleActiveConsumer calls notifyActiveConsumerChanged() from scheduleReadOnActiveConsumer(); in the non-persistent path that method was a no-op.

Clients using ConsumerEventListener on non-persistent Failover topics therefore never got becameActive / becameInactive on failover.

Modifications

In NonPersistentDispatcherSingleActiveConsumer.scheduleReadOnActiveConsumer(), call notifyActiveConsumerChanged(getActiveConsumer()). Non-persistent topics have no cursor, so there is no rewind/read step like on persistent topics.
Extend NonPersistentDispatcherFailoverConsumerTest for add/remove failover, priority-based active selection, and adding a consumer to a closed dispatcher.

Verifying this change

• Make sure that the change passes the CI checks.

This change added tests and can be verified as follows:

NonPersistentDispatcherFailoverConsumerTest.testActiveConsumerChangeNotifications
NonPersistentDispatcherFailoverConsumerTest.testHigherPriorityConsumerBecomesActive
NonPersistentDispatcherFailoverConsumerTest.testAddConsumerWhenClosed

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• Dependencies (add or upgrade a dependency)
• The public API
• The schema
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• The threading model
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• Anything that affects deployment