ci: Improve GitHub Action modularity (typos, migrations, check_style, etc)

[notpeter]

• Switch to using the official typos GitHub Action
• Move the typos check into actions/check_style
• Move Squawk Postgres migration check out of actions/check_style file into ci.yml
• actions/check_style can now be run on stateless/linux runners (previous required self-hosted MacOS runner)
• ci.yml: Split old style into checks into those that can run statelessly (linux) and everything else into a new migration group which benefit from the full git checkout available on the MacOS runners.
• ci.yml: Move Check unused dependencies from style to linux_tests

Docs:

Release Notes:

• N/A