Send connection keepalive pings once per minute to prevent stream termination while awaiting long-running jobs (#7755)

Author: hoisinberg

cirq-google/cirq_google/cloud/quantum_v1alpha1/services/quantum_engine_service/transports/grpc_asyncio.py

@@ -299,6 +299,10 @@ def __init__(
                 options=[
                     ("grpc.max_send_message_length", -1),
                     ("grpc.max_receive_message_length", -1),
+                    # Send connection keepalive pings once per minute
+                    ("grpc.keepalive_time_ms", 60 * 1000),
+                    # Allow unlimited keepalive pings in between data frames
+                    ('grpc.http2.max_pings_without_data', 0),
                 ],
             )