This will allow users to customize the stream ack deadline of the initial streaming pull request. This can be useful if a subscriber is experiencing high latencies for certain messages because the messages are not being received by the subscriber despite being sent by pubsub, maybe because of high network latency or the message was lost. When the stream ack deadline is expired, if pubsub is not aware of the message having arrived to the subscriber, pubsub will redeliver the message. The drawback of setting the deadline too low is that it may incur in redeliveries if the original message ends up arriving.