Objects that share a mesh with a VFX become uninteractable

I thought we already had an issue for this but I can't find it.

Basically, if you assign w/w_iron_dagger.nif to the VFX_DestructCast static and cast a destruction spell, all weapons using that mesh (i.e. all iron daggers) can no longer be interacted with. This is made worse by animation.addVfx allowing this assignment to happen to any model at runtime.

!2214 (merged) introduced this issue by setting Mask_Effect on every osg::Drawable in a VFX tree. These drawables are shared between every instance of the model because SceneManager::cloneNode does a shallow copy of sorts.