Function evosim::mutate::geno_mutate::get_movevec

fn get_movevec(
    index: usize,
    old_size: [f32; 2],
    new_size: [f32; 2]
) -> Option<([f32; 2], [f32; 2], [f32; 2])>

if a block has its size changed, all its subnode will have their position changed

Base on the changes of a node, return how much and which direction all its subnodes will move.

outputs front, left, right movement vector for input node (facing outward to the root node)