2104 - collision_grid_update

Updating collision_grid_update for the various input cases highlighted a few issues that we need to resolve. There’s no tracking of filtered out instances (e.g. the live_instances bit set for enemy instances.) Got the basic update working and visualized the data being stored to help sort out the issues. On the left are the hero instances and hero bullets. On the right are the enemy instances and enemy bullets. The play area is divided into 16 slices vertically. The number of instances overlapping that a slice is stored, and the indices of the specific instances are stored per slice, for later more fine-grained collision testing.