feat: Allow pinning dependency to a specific commit

[BatteredBunny]

• Adds support for pinning to a specific commit via git_commit=
• Sets up infra for pytest tests and adds 2 tests which test tag & commit pinning along with pin changing behaviour.
• Adds github action workflow which runs the tests.
• Fixes infinite recursion bug in mama deploy

For tests it uses https://github.com/BatteredBunny/MamaExampleRemote repo since the original was missing tags to test.