Increase default value of pubsub backoffPolicy totalBackoff

[istreeter]

The current default value is 10 seconds. This means if the collector cannot publish to pubsub within 10 seconds then an event is dropped and an error is logged.

It is a principle of the collector that should never drop any event, but instead should continue to accept events in the hope that downstream errors are transient. A better value for backoffPolicy.totalBackoff is 9223372036854, which is the largest allowed value in milliseconds. This will prevent data loss in the case when the collector is publishing events to pubsub more quickly than pubsub allows.

In the meantime, users can override the default value to 9223372036854 in their config file.

[istreeter]

Linking to relevant conversation on Discourse. We should also make the RPC timeouts configurable, and use a larger default for maxRpcTimeout.