[Improvement] Extend event size threshold metric configuration to any number of levels

### Code of Conduct

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

### Search before asking

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

### What would you like to be improved?

In current codebase, it has three levels metrics of `rss.server.event.size.threshold.l1/l2/l3`, but this is not enough for production env.

We hope to extend event size threshold metric configuration to any number of levels, like introducing a new config option:
`rss.server.event.size.threshold.level.ranges=20k,1m,10m,100m,1g,10g,` which could cover the multiple levels for better configuring the writing threads number or single buffer flush size.

### How should we improve?

_No response_

### Are you willing to submit PR?

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

Start by locating the existing rss.server.event.size.threshold.l1/l2/l3 configuration and tracing how those thresholds affect writing-thread counts or single-buffer flush sizes. Define how an arbitrary rss.server.event.size.threshold.level.ranges list should map to metrics and verify that existing three-level behavior remains covered.

Written by the indexing model from the issue text.