refactor: remove stream_options from model adapters and consolidate t…

[OhYee]

…est helpers

Removed stream_options parameter from CrewAI, Google ADK, and PydanticAI model adapters as it was causing issues with non-streaming requests and each framework handles usage information internally. Consolidated test helper functions from separate helpers.py file into conftest.py to improve test organization and maintainability.

移除 CrewAI、Google ADK 和 PydanticAI 模型适配器中的 stream_options 参数，因为它在非流式请求中造成问题，且每个框架都内置处理用量信息。将测试辅助函数从独立的 helpers.py 文件合并到 conftest.py 中，以改善测试组织和可维护性。

Change-Id: Ia38c6fe5d592af637e16d2307dda826832a19665

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