Add support for 3.12 in workflow files and configs

[VersusFacit]

resolves #1104

Problem

Adding Python 3.12 should pass a series of tests

✅ pytest tests/unit local
✅ pytest tests/functional local
✅ dbt seed && dbt run in a local jaffle shop using plain pip install dbt-redshift with 3.12 active
✅ smoke testing run using test-bundle on snowflake against the jaffle-shop-base scenario with 3.12.X active
✅ GHA workflow involving integration tests
✅ release workflow still works

Solution

No code changes required per my testing above.

Checklist

• I have read the contributing guide and understand what's expected of me
• I have run this code in development and it appears to resolve the stated issue
• This PR includes tests, or tests are not required/relevant for this PR
• This PR has no interface changes (e.g. macros, cli, logs, json artifacts, config files, adapter interface, etc) or this PR has already received feedback and approval from Product or DX

[github-actions]

Thank you for your pull request! We could not find a changelog entry for this change. For details on how to document a change, see the dbt-bigquery contributing guide.

[VersusFacit]

GHA workflow involving integration tests: https://github.com/dbt-labs/dbt-bigquery/actions/runs/10328180014/job/28594380285

release workflow: https://github.com/dbt-labs/dbt-bigquery/actions/runs/10328200073