Schema validations to match Java

### Search before asking

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

### Description

Add missing schema validations in SchemaBuilder::build() to match Java's Schema.normalizeColumns():
* reject duplicate PK columns
* require auto-increment columns to be INT/BIGINT and not part of the primary key
* require a primary key when auto-increment is used
* reject empty/whitespace column names and constraint names
* etc that makes sense in the current state

### Willingness to contribute

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