Enable ability to send data in proto format

[snuyanzin]

Enable writing data in proto format, currently it is happening via JSON
based on experiments under the hood bigquery storage api makes transformation from json to proto and it consumes significant amount of time

[snuyanzin]

cc @RyanSkraba

[RyanSkraba]

Thanks! This should probably be the default, right? There's little reason to prefer the JSON format over the proto format for most of our use cases.