Mistral AI support for Spring AI

[ricken07]

Hi,
for a while I've taken the initiative to work on the implementation of MistralAI support by SpringAI on the 'mistral-ai' branch you can see the progress.
@markpollack @tzolov can you take a tour to see

[tzolov]

Now we have full Mistral AI support (@ricken07 thanks for the contributions!)
You can more in the reference docs:

• Mistral AI Chat Completion - sync and streaming
• Mistral AI Embedding
• Mistral AI Function Calling - Note that currently Mistral AI does not support parallel function calling!