Make chunk visuals load through the VisualResourceIdentifier instead of exact paths

[hhyyrylainen]

as this will make renaming files possible without breaking save compatibility

https://github.com/Revolutionary-Games/Thrive/blob/4174a44e6ca7e02e71bf47b59db5771af3d3f808/src/microbe_stage/Spawners.cs#L225

Update: I realized that the CollisionShapeLoader component has a hardcoded path to a physics data object. Meaning that just these changes aren't sufficient to protect the chunks from save breakage when moving resource files around. So in addition the physics loading system should get a similar fix.