Revisit typing of fromActor

[christoph-fricke]

The fromActor service creator should be used to connect a machine to an actor that accepts subscribe events, i.e. a publisher.

The current implementation of fromActor creates some type errors when the helper function is actually used. Some thinks to keep in mind:

• A received actor might publish more event than the machine is interested in.
• A machine can handle more events than the events published by the actor.
• Can we fully type the events that are receivable by the actor?

These have an influence on the type definitions for the machine and actor.

Furthermore, it might be a good idea to send a state update of the actor as an event back to the machine.