Update to Mistral Python SDK v1.0.1

[mor10]

Update Mistral Python SDK to v1.0.1 and refactor all Mistral cookbooks and Python samples to match new version.

Main changes:

• mistralai version updated in requirements.txt
• Single import of Mistral provides all functionality
• Mistral() method has no endpoint parameter. Instead uses server_url
• Chat responses come from client.chat.complete() method
• Streaming responses come from client.chat.stream() method
• Chat messages updated to JSON format
• Function calling requires Mistral-large-2407
• Streaming response object handling has been updated for better error avoidance