test `read_gbq` with `dryRun` in `configuration` parameter

[WillianFuks]

Hello,

Recently a question featured on SO asking about running a read_gbq job with dryRun settings defined as True.

As it turns out, for what I could check, currently we can send query definitions but everything defined outside of query is discarded.

I wonder if it would be possible to also consider updating other values such as dryRun.

kwargs should probably be able to receive arguments such as configuration={"query": {...}, "dryRun": True}

and run_query probably would have to process job_config.update(config).

Best,

Will