[core] fix test_streaming_generator_backpressure on windows

[rueian]

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[gemini-code-assist]

Code Review

This pull request adds Windows-specific error handling when executing driver scripts in streaming generator backpressure tests, catching and logging subprocess.CalledProcessError on Windows while re-raising it on other platforms. The reviewer suggests refactoring this repetitive try-except block into a helper function _run_string_as_driver to reduce code duplication and improve maintainability across the multiple test cases.

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