[FEAT] Provide guidance how to use BigQuery Community UDFs in `bqutil` dataset

**Is your feature request related to a problem? Please describe.**

BigQuery has a list of community-contributed UDF definitions [here](https://github.com/GoogleCloudPlatform/bigquery-utils/blob/1986a2dcbee1fb995dd5717563fce52bfa8087a3/udfs/community/README.md#json_extract_keys).

For demo purposes, these are hosted by BigQuery in a `bqutil` dataset, but [their docs](https://github.com/GoogleCloudPlatform/bigquery-utils/blob/1986a2dcbee1fb995dd5717563fce52bfa8087a3/udfs/README.md#bigquery-udfs) say:

> [!WARNING]
> Do not directly reference any bqutil UDFs in your production environment. You should instead [deploy these UDFs](https://github.com/GoogleCloudPlatform/bigquery-utils/blob/1986a2dcbee1fb995dd5717563fce52bfa8087a3/udfs/README.md#deploying-the-udfs) into your production environment.

We should provide guidance how to deploy these UDFs and utilize them with Fusion.

**Is your feature request related to a particular component of the dbt Fusion Engine**
- [ ] CLI Features
- [ ] Adapter or Database Driver Features
- [x] SQL Understanding Features
- [ ] VS Code extension

**Additional context**
Originally discussed in https://github.com/dbt-labs/dbt-core/issues/13892