[improve][broker] Skip system cursor when check inactive cursor.

[horizonzy]

Motivation

PersistentTopic#checkInactiveSubscriptions skips built-in system subscriptions such as the compaction subscription when deleting expired inactive subscriptions. However, subscriptions configured through additionalSystemCursorNames are also treated as system cursors elsewhere, but were not skipped by this expiration cleanup path. As a result, an additional system cursor could be deleted when it became inactive past the subscription expiration threshold.

Modifications

• Updated PersistentTopic#checkInactiveSubscriptions to skip subscriptions identified by isSystemCursor(subName) instead of only checking the compaction subscription.
• Extended PersistentTopicTest#testCheckInactiveSubscriptions to configure an additionalSystemCursorNames entry and verify that the corresponding subscription is not deleted during inactive subscription cleanup.

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