Add Homebrew release as the final step of the release

[emmyoop]

Homebrew releases should happen after we successfully release to GitHub and PyPI. This will require a central workflow to actually release the formulae and then a change in each repo we release (dbt-core, dbt-snowflake, etc) to the release.yml file.

Release to homebrew if:

1. This is not a test run
2. The release was otherwise successful
3. We are not releasing dbt-spark

Unknowns

1. Should we release every pre-release? Only some?
2. How can we determine if this should be marked as latest? Fix latest tag in GitHub releases #73 might help inform this.
3. Is there a way to test this?

Current release workflow live in homebrew-dbt: formula.yml

This is to prevent this from happening again.

[emmyoop]

This makes this most sense to be it's own workflow as opposued to adding to the current workflows. But I'm not really sure it should live in here or just be a step in the existing release flows in each repo (ex: dbt-core release.yml) where we callout to formula.yml.