fix(bigquery): route JOB_CREATION_REQUIRED through fast query path

[jinseopkim0]

Routes queries under JobCreationMode.JOB_CREATION_REQUIRED to the fast query path (jobs.query API / 1 RPC) to avoid the slow fallback path (jobs.insert API / 2 RPCs).

https://docs.cloud.google.com/bigquery/docs/reference/rest/v2/jobs/query#QueryResponse says:

object (JobReference)

Reference to the Job that was created to run the query. This field will be present even if the original request timed out, in which case jobs.getQueryResults can be used to read the results once the query has completed. Since this API only returns the first page of results, subsequent pages can be fetched via the same mechanism (jobs.getQueryResults).

If jobCreationMode was set to JOB_CREATION_OPTIONAL and the query completes without creating a job, this field will be empty.

Thus, routing JOB_CREATION_REQUIRED through the fast path is preferred.

b/522363981

[gemini-code-assist]

Code Review

This pull request enables fast query support when the job creation mode is set to JOB_CREATION_REQUIRED in QueryRequestInfo. This allows queries with this configuration to execute via the fast query path, returning a TableResult directly (with both JobId and QueryId populated) rather than creating a separate job. Unit and integration tests have been updated to reflect and verify this behavior. I have no feedback to provide.