[Feature] [JavaAPI] Get-started a runnable example

### Search before asking

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

### Motivation

The best way to have a basic view of paimon is to run a complete example in java api. But the document of java api now is not friendly because it's hard to get it work for new learner. Maybe we need a complete runnable example to help someone interested in donating code for paimon.
Maybe a class with "WAREHOUSE=~/tmp/paimon-dir", methods runnable like createCatalog, read, write and so on..

### Solution

_No response_

### Anything else?

_No response_

### Are you willing to submit a PR?

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