tests: simplify stune's boosted utilization signal test
tests: simplify stune's boosted utilization signal test

Trappy 5.2 can operate on a window of a trace and can do floor
division.  Leverage that to simplify the boosted utilization signal test
and make it more "barty".

credp/lisa,bjackman/lisa,joelagnel/lisa,joelagnel/lisa,credp/lisa,ARM-software/lisa,credp/lisa,ARM-software/lisa,ARM-software/lisa,ARM-software/lisa,credp/lisa,arnoldlu/lisa,arnoldlu/lisa,bjackman/lisa,mdigiorgio/lisa,mdigiorgio/lisa,JaviMerino/lisa