[Bug] be内存持续增加，直至无响应

### Search before asking

- [x] I had searched in the [issues](https://github.com/apache/doris/issues?q=is%3Aissue) and found no similar issues.

### Version

3.1.4

### What's Wrong?

be节点运行一段时间发现内存不足，重启后恢复正常，一天左右再次内存不足。服务器负载也都是在一个较低水平。
查看日志发现UntrackedMemory占了90%以上的内存。
导出jeheap如下图，butil ResourcePool add_block在持续增加，且无回落趋势。怀疑存在内存泄露问题

### What You Expected?

内存可被正常回收

### How to Reproduce?

_No response_

### Anything Else?

_No response_

### Are you willing to submit PR?

- [ ] Yes I am willing to submit a PR!

### Code of Conduct

- [x] I agree to follow this project's [Code of Conduct](https://www.apache.org/foundation/policies/conduct)

Start with the BE logs and the supplied jeheap profile for version 3.1.4, focusing on UntrackedMemory and the butil ResourcePool add_block allocation path. Establish a reproducible workload or allocation trace, then determine why allocations keep increasing without returning. Done means the cause is identified and memory remains reclaimable during sustained operation.

Written by the indexing model from the issue text.