Is your feature request related to a problem? Please describe.

Need opt-in catch-alls for workflows, activities, signals, and queries.

Describe the solution you'd like

Should be able to register only one workflow as "dynamic" and it is given the name as a string as the first arg, then *args: Payload as second arg. This means we also need to provide the users of a workflow access to their payload converter to convert those.

Need to do the same for activity.

For signal and query handlers, we already have dynamic=True, but we foolishly allow already-decoded args. Ideally, we would change to require payloads. But since that may be a breaking change, we should just args hinted as payloads pass through unconverted.