[fix][broker] Recover bucket delayed delivery tracker asynchronously to avoid blocking dispatcher threads

[void-ptr974]

Fixes #26103

Motivation

BucketDelayedDeliveryTracker is lazily created from the broker dispatch path
when the first delayed message needs a delayed delivery tracker.

For the bucket implementation, tracker creation also recovers delayed bucket
snapshots. This recovery can depend on metadata or storage operations, but it was
previously waited for synchronously during tracker creation.

As a result, a dispatcher thread could be blocked while holding the dispatcher
lock. If bucket snapshot recovery is slow, dispatch for the current subscription
is stalled, and other tasks queued on the same broker-topic worker can also be
delayed.

Modifications

• Add an asynchronous tracker creation path to DelayedDeliveryTrackerFactory.
• Recover bucket delayed delivery snapshots asynchronously before installing the
  tracker into the dispatcher.
• Keep delayed messages pending while tracker creation is in progress, and pause
  dispatch until the tracker is ready.
• Replay pending delayed messages when tracker creation fails or when their
  delivery time has already elapsed.
• Fall back to the in-memory delayed delivery tracker when bucket recovery fails
  or times out.
• Clean up pending delayed messages on dispatcher close/unload, and close
  trackers that complete after they are no longer needed.
• Add lifecycle logs for tracker creation start, pending creation, completion,
  failure, fallback, and stale tracker cleanup.
• Add tests for async bucket recovery, fallback behavior, dispatcher
  close/clear/replay behavior, and a broker-path delayed message scenario using
  the real bucket tracker.

Verifying this change

• Make sure that the change passes the CI checks.

This change added tests and can be verified as follows:

• ./gradlew :pulsar-broker:test --tests org.apache.pulsar.broker.delayed.DelayedDeliveryTrackerFactoryTest
• ./gradlew :pulsar-broker:checkstyleMain :pulsar-broker:checkstyleTest
• git diff --check

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

• 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

This changes delayed delivery tracker creation from synchronous recovery on the
dispatcher path to asynchronous recovery with dispatcher-side pending state and
replay handling.