[VoiceLive]Support explicit None values in RequestSession serialization

[xitzhang]

Description

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• The pull request does not introduce [breaking changes]
• CHANGELOG is updated for new features, bug fixes or other significant changes.
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Testing Guidelines

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[Copilot]

Pull request overview

This PR adds support for explicit None value serialization in the RequestSession model, enabling scenarios where turn_detection=None needs to be sent as "turn_detection": null in WebSocket messages rather than being omitted. The change updates the package to version 1.2.0b3 (beta status) and bumps the azure-core dependency to 1.36.0.

Changes:

• Extended RequestSession class to track explicitly set None values and include them in serialization
• Updated test to use turn_detection=None instead of {"type": "none"}
• Bumped version to 1.2.0b3 and changed development status from Production/Stable to Beta
• Updated minimum azure-core dependency from 1.35.0 to 1.36.0

Reviewed changes

Copilot reviewed 5 out of 5 changed files in this pull request and generated 6 comments.

Show a summary per file

File	Description
sdk/ai/azure-ai-voicelive/azure/ai/voicelive/models/_patch.py	Adds RequestSession extension with _explicit_none_fields tracking and custom as_dict method to preserve explicit None values
sdk/ai/azure-ai-voicelive/tests/test_live_realtime_service.py	Updates test to use turn_detection=None instead of {"type": "none"}
sdk/ai/azure-ai-voicelive/pyproject.toml	Updates development status to Beta and azure-core dependency to 1.36.0
sdk/ai/azure-ai-voicelive/_version.py	Changes version from 1.2.0 to 1.2.0b3
sdk/ai/azure-ai-voicelive/CHANGELOG.md	Documents the new feature and dependency update for version 1.2.0b3

[github-actions]

API Change Check

APIView identified API level changes in this PR and created the following API reviews

azure-ai-voicelive