Create server_streaming.py

[zinccat]

This pull request adds the server_streaming.py example for the high-level API.

The server_streaming.py file is created under the examples/high_level_api/ directory. It contains an implementation of a server streaming example using the high-level API. The code sends messages through an HTTP POST request to "http://localhost:8000/v1/chat/completions" and processes the response. If the stream is set to non-streaming mode, the content of the response will be printed. Otherwise, the code performs streaming processing on the response and prints the parsed content.

This pull request aims to provide a practical example of server streaming using the high-level API, showcasing how to interact with an HTTP server and handle responses.

[AlessandroSpallina]

What is the purpose of this example? Is there a way to get a real streaming? I mean, starting to show the user an output while the LLM behind the REST server is still processing?