[fix][broker] Prevent backlog quota cursor updates during topic close

[Denovo1998]

Follow-up to #25684

Motivation

BacklogQuotaManager already skips backlog quota handling when a topic is fenced or closing/deleting. However, the previous guard only checked the topic state when entering handleExceededBacklogQuota.

If a topic starts closing after that initial check but before the eviction path mutates the slowest cursor, backlog quota eviction can still call skipEntries or markDelete while the close/delete path is tearing down the same topic. This follow-up hardens that race without changing the existing fenced-topic behavior from #25684.

Modifications

• Recheck PersistentTopic#isClosingOrDeleting() immediately before direct cursor mutations in backlog quota eviction.
• Stop size-based eviction before ManagedCursor#skipEntries if the topic starts closing.
• Stop non-precise time-based eviction before ManagedCursor#markDelete if the topic starts closing.
• Clarify the existing fenced/closing skip comment so transient fenced topics are not described as entries being discarded.
• Add a no-op @VisibleForTesting hook to coordinate deterministic race reproduction without changing production behavior.
• Add real broker/topic race tests that close a topic after the initial backlog quota guard but before cursor mutation, and verify the cursor mark-delete position does not move.

Verifying this change

• Make sure that the change passes the CI checks.

This change added tests and can be verified as follows:

• Added BacklogQuotaManagerTest.testSizeBacklogEvictionRaceWithTopicCloseDoesNotSkipEntries
• Added BacklogQuotaManagerTest.testTimeBacklogEvictionRaceWithTopicCloseDoesNotMarkDelete

Verified locally with:

./gradlew :pulsar-broker:test --tests "org.apache.pulsar.broker.service.BacklogQuotaManagerTest.testSizeBacklogEvictionRaceWithTopicCloseDoesNotSkipEntries" --tests "org.apache.pulsar.broker.service.BacklogQuotaManagerTest.testTimeBacklogEvictionRaceWithTopicCloseDoesNotMarkDelete"
./gradlew :pulsar-broker:test --tests "org.apache.pulsar.broker.service.BacklogQuotaManagerTest"
./gradlew :pulsar-broker:spotlessCheck :pulsar-broker:checkstyleMain :pulsar-broker:checkstyleTest
git diff --check

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

[Denovo1998]

@lhotari @merlimat @dao-jun @nodece @Technoboy- PTAL.