Add support for Short query optimized mode in BigQuery

Would it be possible to add support for "Short query optimized mode" in BigQuery to the Ruby SDK?

**Is your feature request related to a problem? Please describe.**
The BigQuery library does not support [Short query optimized mode.](https://cloud.google.com/bigquery/docs/running-queries#short-query-optimized)

**Describe the solution you'd like**
Add support to the client SDK to perform queries that make use of the Short query optimized mode. With the other SDKs (Python, Javascript, et al), this was done through an env variable.