Add support of limit scan

### Search before asking

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

### Motivation

I’m currently working on [fluss-datafusion](https://github.com/zuston/fluss-datafusion) and would like to expose some example data using LIMIT. However, I haven’t found an existing implementation for this in the project, so I’m happy to contribute it.

That said, the current scanner abstraction makes this a bit complex. The logic between the log scanner and the KV scanner appears quite similar, and it might be worth considering whether these two scanners could be unified.

I’d appreciate any guidance or suggestions on how best to approach a refactor in this area, especially with respect to simplifying the scanner abstraction while keeping the design clean and extensible.

### Solution

_No response_

### Anything else?

_No response_

### Willingness to contribute

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