Restore behavior which persists quantum_run_streams indefinitely (#7527)

#7500 modified the
`quantum_run_stream` method definition by changing the `timeout`
argument from `timeout: float | None = None` to `timeout: float | object
= gapic_v1.method.DEFAULT`. Setting `timeout=None` is interpreted as
having no timeout at all, whereas `timeout=gapic_v1.method.DEFAULT` uses
the framework-supplied default value of 60s. For bidirectional streams,
the `timeout` is used to set the lifetime of the entire stream, causing
batches of jobs which cumulatively take more than 60s to fail with
`DEADLINE_EXCEEDED` errors. This change sets `timout=None` explicitly,
restoring the behavior previously obtained via the default argument.

Author: hoisinberg

cirq-google/cirq_google/engine/stream_manager.py

@@ -205,9 +205,9 @@ async def _manage_stream(
         """
         while True:
             try:
-                # The default gRPC client timeout is used.
                 response_iterable = await self._grpc_client.quantum_run_stream(
-                    _request_iterator(request_queue)
+                    _request_iterator(request_queue),
+                    timeout=None,  # Persist the stream indefinitely.
                 )
                 async for response in response_iterable:
                     self._response_demux.publish(response)