[Feature] Support BigQuery Dataframes on dbt-BigQuery

[amychen1776]

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 functionality, rather than a Big Idea better suited to a discussion

Describe the feature

We want to support BigQuery DataFrames on the dbt-bigquery adapter as an alternative way to execute python models on dbt-bigquery. The benefit of this is users can now choose to either run python models on a service external to BigQuery (Dataproc) or directly on BigQuery using the python API.

• Both the table and incremental materializations will be supported as part of the implementation. Which incremental strategies will be dependent on what can be supported via DataFrames but the desire is to support all the existing BQ incremental strategies along with on_schema_change inputs if possible.
• Users will be able to input a new config field submission_method to define where the python model is executed (see dbt-databricks for example).
• The initial feature ship will be under a behavior flag to ensure a seamless user experience with no regressions. Once users have it set to true, they will be able to pass in the submission method and execute on BigQuery Dataframes.

Describe alternatives you've considered

No response

Who will this benefit?

All BigQuery users who want to keep their data on the BigQuery service still use Python models.

Are you interested in contributing this feature?

This will be a joint effort with the BigQuery and dbt Labs team.

Anything else?

No response