this draft fills in the structure how to get from an invocation
of the engine service to the starting of actual CalcStream instances.
Basically the EngineService implementation is repsonsile to
instruct the Segmentation to provide a suitable Dispatcher.
instead of (ab)using the Timings spect for a
runtime switch, better use the existing
MockInjector facility and thus turn the
mock engine mode into a global switch
