[Feature] Support custom GCS bucket subdirectories for Dataproc

[pbotros]

Is this your first time submitting a feature request?

• I have read the expectations for open source contributors
• I have searched the existing issues, and I could not find an existing issue for this feature
• I am requesting a straightforward extension of existing dbt-bigquery functionality, rather than a Big Idea better suited to a discussion

Describe the feature

Currently, DBT-Bigquery writes Python model files for Dataproc to gs://<gcs bucket>/<model file name>, which can conflict if multiple users (e.g. dev users, CI runs, etc.) concurrently utilize the same GCS bucket.

Instead, it'd be nice for a subdirectory to be optionally configured, to write to gs://<gcs bucket>/<gcs subdirectory>/<model file name> instead.

Describe alternatives you've considered

N/A

Who will this benefit?

Users that want to share a single GCS bucket across multiple concurrent use cases (CI, dev, etc.)

Are you interested in contributing this feature?

Yes

Anything else?

No response

[pbotros]

Let me know if this feature request sounds reasonable; if so, I'm happy to contribute it. I anticipate this should be a small change.