Fix data_race condition in WindmillStreamSenderTest

[parveensania]

Instead of memoizing Backoff constructed instance which is not thread-safe, memoize the builder config instead and return isolated BackOff instance for each individual stream.

[gemini-code-assist]

Summary of Changes

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This pull request addresses a data race condition identified in the Windmill stream sender logic. By refactoring the initialization of the backoff mechanism, the implementation now avoids sharing non-thread-safe instances across streams, instead generating isolated instances from a cached configuration.

Highlights

• Thread-safety improvement: Replaced the memoized BackOff instance with a memoized FluentBackoff configuration to ensure thread-safe creation of backoff instances for individual streams.

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[gemini-code-assist]

Code Review

This pull request refactors the initialization of grpcBackOff in GrpcWindmillStreamFactory to memoize the FluentBackoff configuration instead of the BackOff instance. A review comment identifies inconsistent indentation in the refactored code and provides a suggestion to align it with the project's style.

[github-actions]

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[parveensania]

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[github-actions]

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R: @tvalentyn added as fallback since no labels match configuration

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[damccorm]

Thanks!