Spring-ai Replace the OutputParser by a StructuredOutputConverter API

 - Old OutputParser, BeanOutputParser, ListOutputParser and MapOutputParser classes are depredated
   in favour of the new StructuredOutputConverter, BeanOutputConverter, ListOutputConverter and
   MapOutputConverter implementations.
   Later are drop-in replacements for the former ones, and provide the same functionality.
 - Keep the existing parser package and classes for backward compatibility.
 - Adjust the PromptTemplate for backward compatibility
 - Update all existing tests to use the new Structured Output API.
 - Improve the Adoc structured output documentation.

Comment From: markpollack

edited the docs. Changed the setter in PromptTemplate to be set/getOutputConverter.

Merged in a49a2d213f1d8de2429101b43f047a776b223b00