Fix flaky test_execution test

[henry3260]

Why:

The test_execution test is flaky due to a race condition. When the worker raises the intended RuntimeError, it crashes, causing the LocalExecutor to immediately respawn a new worker to maintain parallelism.

This creates an infinite crash-and-respawn loop if the new worker picks up the failing task again. As a result, executor.end() hangs (times out) because it cannot successfully join the processes while new ones are constantly being spawned.

How:

I introduced a has_failed_once flag to ensure the worker raises the RuntimeError only once. Subsequent executions will return successfully. This prevents the infinite respawn loop, allowing the worker to shut down gracefully and executor.end() to finish without timing out.

closes: #45329

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