Add config option for event stream http routes

Much like our other uses of http, the event stream code needs to be provided a mapping from the expected hostnames to the url we need to send the request to in production. Ideally this would be unified with our existing implementation, but that becomes tedious because event streams and our application are using different versions of the apache http client.

Add a new config option specific to event streams used to pass the routes into the event stream utils.

Bug: T347075