[Feature] Add cofactor check to `Group::new`

[howardwu]

🚀 Feature

struct Group {
    fn new(point: affine) -> Self {
        let output: Group = CS::alloc(point * COFACTOR_INV);
        Self::on_curve_check(output);

        // let output = output * Scalar::constant(COFACTOR);
        let output = output.double().double();

        output
    }
}