Pipe Worker Output Action Names

[steve-the-edwards]

After the addition of debuggingName (here), we weren't effectively using that for Workers because we were still directly overriding toString() in the forwarding action for sendAndAwaitApplication - we need to have that use debuggingName of the original EmitWorkerOutputAction in order to effectively get the debugging names through.

The other change here is just to make EmitWorkerOutputAction debuggingName a constant with the interpolation for worker and key rather than trying to fetch teh class name (we already know the class name!).

Lastly, this doesn't fix #391 as the root problem there is that the action we care about in terms of what we created in the handler we passed to runningWorker is a cascade action that isn't the one pulled off the queue (that's EmitWorkerOutputAction) but only is applied as the 2nd part of the cascade. There is no good solution there as the action is actually created after the worker's output is handled and starts a cascade. In other words, to provide that insight, we have to do that in the interceptors that instrument action cascades.