* change namespaces for agents and extension methods of the Microsoft.Agents.AI.OpenAI package
* remove unnecessary namespace
* remove unused namespaces
* fix compilation issues and rrolled back removed run methods
* sort usings
* add extension methods for AIAgent to work with OpenAI Responses primitives
* Move OpenAIChatClientAgent and OpenAIResponseClientAgent to samples
* sort usings
* sort usings