Replace BepuPhysics with simple collision checks

[enteryournamehere]

This PR replaces Uchu.Physics with a new implementation, using some simple math instead of BepuPhysics to detect collisions.

• Collision checks between a box and a sphere, and between two spheres, are actually correct now. From what I saw during testing, the old method used an axis-aligned bounding box for any shape, resulting in inaccurate trigger areas.
  • Collision checks between two boxes only check whether any of the vertices are in the other shape, so edge-edge collisions aren't detected. However, this kind of collision is relatively rare, and it'll most likely still result in a vertex-face collision a bit later. Additionally, this function isn't actually needed at the moment - there's currently no box object that should be able to collide with other box objects.
• Although bepuphysics is very fast, this is faster, taking 0ms for Ninjago Monastery where the old code took 2 to 5 ms.
• Removed CylinderBody and CapsuleBody, added SphereBody. (Player is now seen as a sphere with radius 2 instead of as a capsule.)
• Fixed some inaccuracies in the SetPhysicsByPath function.

I've also added a script for death planes in Venture Explorer, which is finally possible now that the collisions are accurate 🎉