[Feature] Support File Index writing

### Search before asking

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

### Motivation

Paimon C++ currently supports reading File Indexes but does not generate them through the table write path.

### Solution

- Align File Index functionality and index format with Java Paimon.
- Design the C++ File Index writer interfaces and integrate File Index generation into the table write path.

### Anything else?

This is a sub-issue of #158.

### Are you willing to submit a PR?

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