feat: added Azure OpenAI chat compeltion, environment variables sample and update self.thread._thread_id method in semantic kernel agent sample

[xuhaodev]

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Fixes #<issue_number_goes_here> 🦕

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[xuhaodev]

hi A2A team,
This PR improves the Semantic Kernel A2A agent sample by adding support for Azure OpenAI endpoints and providing environment variable examples. It also updates the usage of the self.thread._thread_id method to self.thread.id. All functionalities have been tested and are working correctly.
Please review. Thanks