Prefix Lookup supports limit to reduce the impact of hot keys

### Search before asking

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

### Motivation

When using prefix lookup queries, multiple results may be returned. A large amount of data under hot keys can cause query or service instability. We can reduce the impact of hot keys by supporting a limit on the maximum number of results returned for prefix lookups.

### Solution

_No response_

### Anything else?

_No response_

### Willingness to contribute

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

Start by locating the prefix lookup API and its existing tests in the Fluss codebase. Determine where a maximum result limit belongs and how its behavior should be specified, then verify that prefix lookups never return more than the configured limit and that relevant tests cover hot-key queries.

Written by the indexing model from the issue text.