2110 - Collect damage events

Also output context struct for copy/paste. Implement collision_damage_update to collect up damage events. Keep it pretty simple: Do A and B have anything on the same slice? If so, for each of the instances on A and B on that slice, Test if each radius overlaps. Oh, I missed this, so next I also need to add: Don’t re-add same collision multiple times if they happen on multiple slices.