Add Ceil/Floor/Round To Interval nodes and SlotToBodyNode

[Xlinka]

• Adds RoundToInterval, FloorToInterval, and CeilToInterval ProtoFlux nodes (float & double variants) under Obsidian/Math — rounds a value to the nearest multiple of a given interval, useful for grid snapping and value binning

• Adds SlotToBodyNode under Obsidian/Avatar — resolves a slot to its BodyNode enum value by walking up to the nearest BipedRig

[Nytra]

SlotToBodyNode looks good, but the Interval nodes aren't really doing anything that isn't already possible

The Interval nodes I think would work better as ProtoFlux functions which will have to wait until they get implemented in Resonite officially Yellow-Dog-Man/Resonite-Issues#564

[fulgenscode]

I was happy to see the interval nodes, but I can see a potential issue if Resonite implements nodes with the same name.

[Xlinka]

I was happy to see the interval nodes, but I can see a potential issue if Resonite implements nodes with the same name.

this has happend before where we just remove the plugin node as its been replaced by first party.

[Nytra]

this has happend before where we just remove the plugin node as its been replaced by first party.

there would be no way to upgrade them, they would just become null

should think about future compatibility a bit