Function rotate_right

src/tree/binary/rb.rs:233–250

右旋操作变换为: Y X / \ / \ X c => a Y / \ / \ a b b c */

(
    mut root: Option<NonNull<Node<K, V>>>,
    y: NonNull<Node<K, V>>,
)

 */
fn rotate_right<K, V>(
    mut root: Option<NonNull<Node<K, V>>>,
    y: NonNull<Node<K, V>>,
) -> Option<NonNull<Node<K, V>>> {
    let mut y = NodeQuery::new(Some(y));
    let p = y.parent();
    let mut x = y.left();
    let a = x.left();
    let b = x.right();
    let c = y.right();
    y.replace(x.node);
    y.set_children(b.node, c.node);
    x.set_children(a.node, y.node);
    if p.is_none() {
        root = x.node;
    }
    root
}

#[test]
fn t_insert() {