generalize dentata-snakes bounce logic into a util function

[TheAfroOfDoom]

Summary

Split from #83

In the upcoming soul event 0 PR, we use the same "bounce-off-walls" logic that the dentata-snakes attack uses to bounce its snake heads / snake tails off the boss fight arena's walls.

This PR converts that function and dentata-snakes' usage of it to take in macro parameters to specify the walls we want the entity to bounce off of and another command_after_bouncing parameter that can be used to run a function if the entity did successfully bounce (optional, can just specify return 0 if you want nothing to happen). The dentata-snakes attack uses this to shake the screen / play a sound effect after successfully bouncing.

We no longer refer to the walls as confusing "top" "bottom" etc., but instead refer to them by their cardinal direction. For example the wall you'd see while facing the +Z direction is the +Z wall.

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Test plan

• dentata-snakes attack still works in-game, bouncing as expected
• screen still shakes + bounce noise still occurs after a snake head bounces off a wall

Reproducing in-game

you can ensure the dentata-snakes attack still works as expected by running:

function _:attack/dentata-snakes

Preview

N/A -- same visuals as before

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Supplemental changes

N/A