[Feature] Improve performance of sort file store for lookup table

### Search before asking

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

### Motivation

Improve the performance of sort file store.

### Solution

_No response_

### Anything else?

_No response_

### Are you willing to submit a PR?

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

Start by locating the sort file store implementation and the lookup-table path in the Paimon codebase. Profile the current lookup-table operations to identify the performance bottleneck, then define and validate an improvement with relevant tests or benchmarks. Done means the sort file store performs lookup-table operations faster without changing expected behavior.

Written by the indexing model from the issue text.