[Feature] Support making use of the native capabilities of models for structure output.

### Search before asking

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

### Description

Currently, when configured `output_schema`, the react agent directly prompt the model to use a specific format, and use an output parser to extract the structured response from the raw model output. This is the only way for models which don't support tool calling or json mode.

For models support tool calling or json mode, we can makes use of these capabilities to generate structured output.

See https://python.langchain.com/docs/how_to/structured_output/ for details.

### Are you willing to submit a PR?

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