[Feature] Support z-order for primary key table

### Search before asking

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

### Motivation

Support z-order for primary key table

### Solution

_No response_

### Anything else?

_No response_

### Are you willing to submit a PR?

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

The issue only identifies z-order support for primary key tables and does not name files, tests, or an implementation path. Start by locating the primary-key table implementation and existing z-order or table-ordering references in the repository. Done is not defined beyond supporting z-order, so the required behavior and tests need clarification before implementation.

Written by the indexing model from the issue text.