Upgrade to Workflow 1.x

[zach-klippenstein]

This is currently blocked by #144, which is in turn caused by https://youtrack.jetbrains.com/issue/KT-40605.

[zach-klippenstein]

Underlying Kotlin issue has apparently been fixed in 1.4.20 dev builds, once those enter EAP we can try it, but not sure when that will be.