Item drops should use regular 3d models instead of raymarching.

[IntegratedQuantum]

The original reason for using raymarching was dumb. If item drops are greedy-meshed then they should not become a bottleneck, since there is a hard limit of 65536 items. And even if they become a bottleneck, then a better fix would be batching them and using raster occlusion culling on them.

This would also open up the opportunity to allow custom item models.