Make Benchmark Trend Slop Threshold configureable

As the UC 4 is computational expensive and is only able to process low loads, the Threshold of 2000 for the Trendslope is too high. E.g. for the load of 2000 and 1 Instance the trend slope is 1200, which indicates that there are a lot of messages not processed.

Therefore it would be useful to make the threshold configureable per use case.