Further simply and consolidate GetGateCount chemistry sample.

[cgranade]

As per @anpaz-msft's comments in #202, it would be good to further consolidate the C# code for the GetGateCount sample. In particular, there's still some duplicated code sections near where each of the Q# operations is run and then converted out to resource estimates by calls to QCTraceSimulator.GetMetric.

[guenp]

Thanks @cgranade for flagging, I'll look into this.