Move configuration out of workflows and eliminate tox as a dependency

[mikealfare]

Problem

There's configuration in both the config files and in the GHA workflows. We use tox on top of this to manage some of the configuration.

Solution

• Move configuration out of GHA workflows and into config files, prioritizing pyproject.toml
• Move configuration out of tox and into config files, prioritizing pyproject.toml
• Remove tox as a requirement

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-snowflake contributing guide.

[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-snowflake contributing guide.

[mikealfare]

This will happen as part of the migration to dbt-adapters