Add granular `ProtocolDAG` progress reporting by compute services

[dotsdl]

As a potential follow-up to #415 and #180, it may be desirable to add in-ProtocolUnit ProtocolDAG progress reporting. This could be accomplished by one or more of the following:

• making use of gufe logging streamed back to server and exposed via the AlchemiscaleClient, approximately as logs are generated by a ProtocolUnit
• by introducing a separate ProtocolDAG/ProtocolUnit progress mechanism in gufe that any execution engine, including alchemiscale, can use to report back execution progress to the server and expose to the user