[Feature] Adapter-specific security advice in docs?

### Is this your first time submitting a feature request?

- [X] I have read the [expectations for open source contributors](https://docs.getdbt.com/docs/contributing/oss-expectations)
- [X] I have searched the existing issues, and I could not find an existing issue for this feature
- [X] I am requesting a straightforward extension of existing dbt-bigquery functionality, rather than a Big Idea better suited to a discussion

### Describe the feature

Add a section to BigQuery adapter docs on recommended security practices

### Describe alternatives you've considered

None

### Who will this benefit?

All users of dbt on BigQuery

### Are you interested in contributing this feature?

I have written a piece on VPC service controls that might be helpful

### Anything else?

https://tempered.works/posts/2024/07/06/preventing-data-theft-with-gcp-service-controls/

Start with the BigQuery adapter documentation and review the linked article on VPC Service Controls. Define the recommended security practices section, verify its guidance against the relevant Google Cloud documentation, and consider the submitted VPC Service Controls material. Done means the BigQuery docs contain an accurate, reviewed security-advice section.

Written by the indexing model from the issue text.