* improve structured output for chat client agent
* add comment to the result property
* remove code duplication and add tests
* refactor the CreateAIAgent extension methods to return specific types, so consumers can avoid unnecessary downcasting.
* fix type and remove unused using.
* add ChatClientAgentRunResponse and move AgentRunResponse to the abstractions package to reuse later.
* seal ChatClientAgentRunResponse
* update xml comment
* remove funcitons from sample
* rename agent for streaming
SergeyMenshykh
3fd5768b34