Spring-ai Improve chat client and advisor observations

• Make ChatClient and Advisor observation logic null-safe
• Simplify naming for Advisor observations
• Include high-cardinality attributes only if a value is present
• Fix condition to include system test to chat client observations
• Add Advisor order information to context
• Streamline usage of enums and utils to reduce hard-coded/duplications
• Fix pending Chroma integration test

Comment From: tzolov

LGTM, thanks @ThomasVitale