Check overlapping triggers handling

[marc1uk]

Currently if a trigger start is within the window of a previous trigger, it's start is shifted to the end time of the previous trigger, but it's end time is not changed. I.e., the two trigger windows remain distinct (trigger window does not get extended, a new one gets added), but the latter trigger window gets shortened.
This may not match ANNIE behaviour if all hefty self-trigger windows are 2us long.
In particular consider how this is handled with the prompt RWM trigger.