[Bug] The Bucket-based delayed queue has serious performance issues

### Search before reporting

- [x] I searched in the [issues](https://github.com/apache/pulsar/issues) and found nothing similar.

### Read release policy

- [x] I understand that [unsupported versions](https://pulsar.apache.org/contribute/release-policy/#supported-versions) don't get bug fixes. I will attempt to reproduce the issue on a supported version of Pulsar client and Pulsar broker.

### User environment

jdk:1.8
pulsar: 2.9(delayed queue cherry-pick from 4.1)

### Issue Description

When I was testing delayed messages with a TPS of 100,000, the maximum delayed time reached to 6 minutes, but I switched to the `InMemoryDelayedDeliveryTracker `implementation and there was no delay at all. I used arthas to trace the method that affects the delay as follows:

> `---ts=2025-08-05 11:34:58;thread_name=BookKeeperClientWorker-OrderedExecutor-60-0;id=761;is_daemon=false;priority=5;TCCL=sun.misc.Launcher$AppClassLoader@18b4aac2
> `---**[1525.23451ms]** org.apache.pulsar.broker.delayed.bucket.MutableBucket:createImmutableBucketAndAsyncPersistent()
> +---[0.00% 0.004104ms ] org.slf4j.Logger:isDebugEnabled() #65
> +---[0.00% 0.001213ms ] org.apache.pulsar.broker.delayed.bucket.DelayedIndexQueue:isEmpty() #70
> +---[0.00% 6.05E-4ms ] org.apache.pulsar.broker.delayed.proto.SnapshotSegment:() #80
> +---[0.00% 0.001309ms ] org.apache.pulsar.broker.delayed.proto.SnapshotSegmentMetadata:newBuilder() #81
> +---[3.14% min=4.16E-4ms,max=0.100719ms,total=47.925984ms,count=100269] org.apache.pulsar.broker.delayed.bucket.DelayedIndexQueue:isEmpty() #86
> +---[3.31% min=4.36E-4ms,max=0.078285ms,total=50.485672ms,count=100268] org.apache.pulsar.broker.delayed.bucket.DelayedIndexQueue:peekTimestamp() #87
> +---[3.93% min=5.26E-4ms,max=0.09415ms,total=59.973353ms,count=100268] org.apache.pulsar.broker.delayed.proto.SnapshotSegment:addIndexe() #94
> +---[18.37% min=6.61E-4ms,max=0.385861ms,total=280.154489ms,count=100268] org.apache.pulsar.broker.delayed.bucket.DelayedIndexQueue:popToObject() #95
> +---[3.13% min=4.25E-4ms,max=0.077715ms,total=47.763836ms,count=100268] org.apache.pulsar.broker.delayed.proto.DelayedIndex:getLedgerId() #97
> +---[3.38% min=4.15E-4ms,max=4.176822ms,total=51.522645ms,count=100268] org.apache.pulsar.broker.delayed.proto.DelayedIndex:getEntryId() #98
> +---[4.17% min=5.25E-4ms,max=0.098286ms,total=63.590418ms,count=100268] org.apache.pulsar.broker.delayed.bucket.MutableBucket:removeIndexBit() #100
> +---[3.01% min=4.1E-4ms,max=0.081268ms,total=45.86729ms,count=100268] com.google.common.base.Preconditions:checkArgument() #102
> +---[0.24% min=4.97E-4ms,max=0.018513ms,total=3.613644ms,count=5000] org.apache.pulsar.common.util.collections.TripleLongPriorityQueue:add() #106
> +---[4.19% min=4.24E-4ms,max=0.11698ms,total=63.957344ms,count=100268] org.roaringbitmap.RoaringBitmap:add() #109
> +---[3.18% min=4.26E-4ms,max=0.093465ms,total=48.53501ms,count=100268] org.apache.pulsar.broker.delayed.bucket.DelayedIndexQueue:isEmpty() #113
> +---[3.36% min=4.53E-4ms,max=0.079834ms,total=51.208435ms,count=100267] org.apache.pulsar.broker.delayed.bucket.DelayedIndexQueue:peekTimestamp() #113
> +---[3.27% min=4.42E-4ms,max=0.202628ms,total=49.945296ms,count=100267] org.apache.pulsar.broker.delayed.proto.SnapshotSegment:getIndexesCount() #115
> +---[0.00% min=9.88E-4ms,max=0.004782ms,total=0.029214ms,count=21] org.apache.pulsar.broker.delayed.proto.SnapshotSegmentMetadata$Builder:setMaxScheduleTimestamp() #116
> +---[0.00% min=7.62E-4ms,max=0.001453ms,total=0.024201ms,count=21] org.apache.pulsar.broker.delayed.proto.SnapshotSegmentMetadata$Builder:setMinScheduleTimestamp() #117
> +---[0.01% min=0.001099ms,max=0.006919ms,total=0.11485ms,count=21] org.roaringbitmap.RoaringBitmap:runOptimize() #125
> +---[0.00% min=6.93E-4ms,max=0.001374ms,total=0.021659ms,count=21] org.roaringbitmap.RoaringBitmap:serializedSizeInBytes() #126
> +---[0.01% min=0.001293ms,max=0.006299ms,total=0.119293ms,count=21] org.roaringbitmap.RoaringBitmap:serialize() #127
> +---[0.00% min=0.001063ms,max=0.002327ms,total=0.040085ms,count=21] com.google.protobuf.UnsafeByteOperations:unsafeWrap() #129
> +---[0.01% min=0.001763ms,max=0.004998ms,total=0.082605ms,count=21] org.apache.pulsar.broker.delayed.proto.SnapshotSegmentMetadata$Builder:putDelayedIndexBitMap() #129
> +---[0.00% min=0.001002ms,max=0.001668ms,total=0.031553ms,count=21] org.apache.pulsar.broker.delayed.proto.SnapshotSegmentMetadata$Builder:build() #140
> +---[0.01% min=0.001733ms,max=0.005025ms,total=0.088917ms,count=21] org.apache.pulsar.broker.delayed.proto.SnapshotSegmentMetadata$Builder:clear() #141
> +---[0.00% min=6.68E-4ms,max=0.001178ms,total=0.019536ms,count=21] org.apache.pulsar.broker.delayed.proto.SnapshotSegment:() #144
> +---[0.00% 0.002128ms ] org.apache.pulsar.broker.delayed.proto.SnapshotMetadata:newBuilder() #152
> +---[0.00% 0.004728ms ] org.apache.pulsar.broker.delayed.proto.SnapshotMetadata$Builder:addAllMetadataList() #153
> +---[0.00% 0.006883ms ] org.apache.pulsar.broker.delayed.proto.SnapshotMetadata$Builder:build() #154
> +---[0.00% 0.013098ms ] org.apache.pulsar.broker.delayed.bucket.ImmutableBucket:() #158
> +---[0.00% 0.001101ms ] org.apache.pulsar.broker.delayed.bucket.ImmutableBucket:setCurrentSegmentEntryId() #160
> +---[0.00% 0.00618ms ] org.apache.pulsar.broker.delayed.bucket.ImmutableBucket:setNumberBucketDelayedMessages() #161
> +---[0.00% 0.001732ms ] org.apache.pulsar.broker.delayed.bucket.ImmutableBucket:setLastSegmentEntryId() #162
> +---[0.00% 0.001285ms ] org.apache.pulsar.broker.delayed.bucket.ImmutableBucket:setFirstScheduleTimestamps() #163
> +---[0.00% 0.001066ms ] org.apache.pulsar.broker.delayed.bucket.ImmutableBucket:setDelayedIndexBitMap() #164
> +---[0.00% 9.01E-4ms ] org.apache.pulsar.broker.delayed.bucket.ImmutableBucket:setSnapshotSegments() #168
> +---[0.00% 6.88E-4ms ] com.google.common.base.Preconditions:checkArgument() #171
> +---[0.00% 6.24E-4ms ] org.apache.pulsar.broker.delayed.proto.SnapshotSegment:getIndexesCount() #173
> +---[0.00% 0.001991ms ] org.apache.pulsar.broker.delayed.proto.SnapshotSegment:getIndexeAt() #173
> +---[0.00% 0.001245ms ] org.apache.commons.lang3.tuple.Pair:of() #174
> +---[0.03% 0.419479ms ] org.apache.pulsar.broker.delayed.bucket.MutableBucket:asyncSaveBucketSnapshot() #176
> `---[0.00% 0.001589ms ] org.apache.pulsar.broker.delayed.bucket.ImmutableBucket:setSnapshotCreateFuture() #178

### Error messages

```text

```

### Reproducing the issue

nohup bin/pulsar-perf produce --auth_plugin org.apache.pulsar.client.impl.auth.AuthenticationToken --auth-params xxxxxxxxxxxxxx -threads 5 -u pulsar://xxxx:6650 -n 4 -s 2048 -r 100000 -dr 1,180 persistent://qlm-tn/delay/topic-delay-1 >producer.log 2>&1 &

### Additional information

_No response_

### Are you willing to submit a PR?

- [ ] I'm willing to submit a PR!

Start with MutableBucket#createImmutableBucketAndAsyncPersistent() and the DelayedIndexQueue methods identified in the Arthas trace. Reproduce the issue with the provided pulsar-perf command at 100,000 TPS, then compare the bucket-based tracker with InMemoryDelayedDeliveryTracker. Done means the delayed queue no longer accumulates the reported multi-minute delay under the stated workload.

Written by the indexing model from the issue text.