[Bug] SnapshotSegmentAbortedTxnProcessorImpl contains thread safety issues

### Search before asking

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

### Version

master

### Minimal reproduce step

There are several thread safety issues in SnapshotSegmentAbortedTxnProcessorImpl class.
examples:
https://github.com/apache/pulsar/blob/529e1ab80998143cfe793c018429e9d2bbee5473/pulsar-broker/src/main/java/org/apache/pulsar/broker/transaction/buffer/impl/SnapshotSegmentAbortedTxnProcessorImpl.java#L374-L376
https://github.com/apache/pulsar/blob/529e1ab80998143cfe793c018429e9d2bbee5473/pulsar-broker/src/main/java/org/apache/pulsar/broker/transaction/buffer/impl/SnapshotSegmentAbortedTxnProcessorImpl.java#L383
https://github.com/apache/pulsar/blob/529e1ab80998143cfe793c018429e9d2bbee5473/pulsar-broker/src/main/java/org/apache/pulsar/broker/transaction/buffer/impl/SnapshotSegmentAbortedTxnProcessorImpl.java#L744

### What did you expect to see?

Multi-threading code should be thread safe.

### What did you see instead?

Non thread-safe code.

### Anything else?

_No response_

### Are you willing to submit a PR?

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

Start by reading pulsar-broker/src/main/java/org/apache/pulsar/broker/transaction/buffer/impl/SnapshotSegmentAbortedTxnProcessorImpl.java, focusing on the referenced lines 374-376, 383, and 744. Trace how these sections are reached concurrently and identify the expected synchronization behavior. Done means the reported thread-safety issues are resolved and verified with appropriate multithreaded regression coverage.

Written by the indexing model from the issue text.