Faster MeshletMesh deserialization

[JMS55]

Objective

• Using bincode to deserialize binary into a MeshletMesh is expensive (~77ms for a 5mb file).

Solution

• Write a custom deserializer using bytemuck's Pod types and slice casting.
  • Total asset load time has gone from ~102ms to ~12ms.
• Change some types I never meant to be public to private and other misc cleanup.

Testing

• Ran the meshlet example and added timing spans to the asset loader.

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Changelog

• Improved MeshletMesh loading speed
• The MeshletMesh disk format has changed, and MESHLET_MESH_ASSET_VERSION has been bumped
• MeshletMesh fields are now private
• Renamed MeshletMeshSaverLoad to MeshletMeshSaverLoader
• The Meshlet, MeshletBoundingSpheres, and MeshletBoundingSphere types are now private
• Removed MeshletMeshSaveOrLoadError::SerializationOrDeserialization
• Added MeshletMeshSaveOrLoadError::WrongFileType

Migration Guide

• Regenerate your MeshletMesh assets, as the disk format has changed, and MESHLET_MESH_ASSET_VERSION has been bumped
• MeshletMesh fields are now private
• MeshletMeshSaverLoad is now named MeshletMeshSaverLoader
• The Meshlet, MeshletBoundingSpheres, and MeshletBoundingSphere types are now private
• MeshletMeshSaveOrLoadError::SerializationOrDeserialization has been removed
• Added MeshletMeshSaveOrLoadError::WrongFileType, match on this variant if you match on MeshletMeshSaveOrLoadError