⚠️ Local Worker will not work with Slack toolkit until this is merged
Support [PEP 604](https://peps.python.org/pep-0604/) Union Types for
tool input param types and return types.
https://github.com/ArcadeAI/arcade-ai/pull/345 introduced PEP 604 Union
Types into our toolkits, but the worker did not support this syntax, so
it was failing on start up if a tool used bar syntax in its return type
(Slack).
Additionally, optionals defined with `Union[T, None]` were already
supported, but didn't have any unit tests, so I added them.
Fixes 2 issues that were causing CI to fail:
- Loading `config` in `eval.py` breaks because no API key can be found
in CI
- Python 3.11+ changed `Union` to `UnionType`
