Correct Collision

Been reworking old collision geometry from our unreal sets without bothering to look at the actual requirements for Unreal. Turns out they're different from what we've got there. This realization comes half way through the set... so this likely means a rework from scratch. Not only for this set but also for the snake temple and likely other old sets as well.

As a note to self... convex only collision geometry is still a thing. So rebuild the shape from lots of simple primitives (this arch for example has 18 pieces). Don't merge collision meshes into one mesh, number them, label them starting with UCX_ for unreal.

This will be one gigantic pain in the a&%"$ in unity as unity does not have that automatic collision recognition on import like unreal does... in unity every individual piece needs to be labeled as collision by hand... might go looking for a script. Someone must have run into similar issues before me.