[Question] How to monitor data latency in DV table query

### Search before asking

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

### Motivation

To improve query performance, in real-time updated scenes, we use the primary key table of Paimon with a deletion vector.
When Flink write task performance is insufficient, the timeliness of data will be affected (L0 files are not visible until they are merged).
Is there any way to monitor the query latency?

### Solution

_No response_

### Anything else?

_No response_

### Are you willing to submit a PR?

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

No files, tests, or entry points are named. Start by reviewing Paimon primary-key tables with deletion vectors and the Flink write path, focusing on when L0 files become visible after merging. Done would require a defined way to measure or monitor query latency, but the issue does not specify the expected mechanism.

Written by the indexing model from the issue text.