fix: correctly cache mesh collision objects - #49

This prevents the current game crashing on reusing collision shapes for enemies

• Remove the collider bulletMesh component data member, since it gets destroyed from one collider but still gets used by another, so it's pretty useless since we're implementing caching.
• Add new shapeCacheId for colliders to store the cache id for the model/mesh when loaded. This isn't deserialized, but instead is set by the enemy spawned when creating an enemy.
• Add new meshDataCache for the collision system to store meshes collision objects.
• Re-order the collision update call to be before any raycast calls

Future work

• We should not use btBvhTriangleMeshShape for dynamic objects (enemies), it's optimized for static environments. Instead, we should use btGImpactMeshShape.