include spark sizes etc in ch8 test

[kowey]

This would make a good wont-fix, but I was thinking it would be nice if people could play with all the bells and whistles on the sample trace.

[MikolajKonarski]

A sensible idea. I think we could add by hand the SparkCounter? events to ch8 and perhaps others and then automatically generate the fine-grained events that are used for the spark histogram and check if we've got it right by validating them with ghc-events. Or manually add the fine-grained events and generate the summary SparkCounter? events --- the automatic procedure would be useful also in case when an eventlog lacks SparkCounters?, but the user wants to visualize it with the spark graphs (not only the spark histogram).