[examples] Data generation via datafaker

### Search before asking

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

### Description

I start to look to data generation for our newly examples. I found the [datafaker](https://github.com/datafaker-net/datafaker) seeems interesting.

- How about generate data for a specific use case, like: data to simulate a Customer 360? we design tables, ex: Customer, Order, Products, etc.
- Use datafaker as our data generation tool? Maybe to have command in fluss-cli or something

Any thoughts about it?

### Willingness to contribute

- [x] I'm willing to submit a PR!
- [x] First version of datafaker usage in example

Start by reviewing the existing examples and the possible fluss-cli entry point, then evaluate the proposed datafaker-based Customer 360 use case and its Customer, Order, and Products tables. Before implementation, define the example scope, schema, and whether generation belongs in the CLI; done means those decisions are settled and a concrete contribution path is identified.

Written by the indexing model from the issue text.