docs: agent metrics code examples improvement

[yesidc]

Description This update refactors the provided examples incorporating the corresponding async blocks. The changes enable the code to be executed seamlessly without any further modifications.

Key Changes: Asynchronous Functionality: Wrapped relevant code in an async def function, allowing for proper asynchronous execution. This eliminates any runtime issues associated with unhandled asynchronous operations.

Evaluator LLM Initialization: Clearly demonstrates the creation of the evaluator_llm object using the LangchainLLMWrapper with the ChatOpenAI model set to gpt-4o. This change improves clarity as the setup of the evaluator was previously not self-explanatory.

Code Readability: Improved formatting and organization of import statements for better readability and maintainability.

[yesidc]

This issue occurs across several parts of the documentation, and it seems to be very confusing, e.g., issue #1925 issue #1939