[fix][broker] Preserve topic initialization failures - #26775

Motivation

PersistentTopic.initialize() loads the namespace policies, then the topic policies, and then removes orphan replication cursors. When any of these stages failed, the failure was logged and ignored, isEncryptionRequired was set to false, and the topic was loaded anyway. The topic then served clients with settings that did not match its configured policies, and it stayed loaded until it was unloaded.

A topic should only become available after its initialization succeeds.

Modifications

• Remove the exceptionally handler in PersistentTopic.initialize(), so a failure in loading namespace policies, loading topic policies or removing orphan replication cursors fails the initialization.
• The existing handling in BrokerService then closes the partially initialized topic and removes it from the topic cache, so a later load retries the initialization. Its log message now describes this as a topic initialization failure.
• Correct the topic policies mock in PersistentTopicTest#testGetReplicationClusters (in org.apache.pulsar.broker.service). The test no longer relies on an ignored initialization failure, and it now verifies that topic-level replication clusters override the namespace-level ones.

Verifying this change

• Make sure that the change passes the CI checks.

This change added tests and can be verified as follows:

• Added PersistentTopicTest#testInitializationFailureClosesTopicAndAllowsRetry (in org.apache.pulsar.broker.service.persistent), which simulates a failure in loading namespace policies, loading topic policies, or removing an orphan replication cursor. It checks that the topic load fails, the topic is removed from the cache and its managed ledger is closed, and that a retry loads the topic with the configured policies applied.

Does this pull request potentially affect one of the following parts:

If the box was checked, please highlight the changes

• Dependencies (add or upgrade a dependency)
• The public API
• The schema
• The default values of configurations
• The threading model
• The binary protocol
• The REST endpoints
• The admin CLI options
• The metrics
• Anything that affects deployment: a topic load now fails when loading its policies or removing orphan replication cursors fails. The load can be retried once the underlying condition recovers.