Function zero_pad

pub fn zero_pad<P, PE>(
    evals: &[P],
    log_evals_size: usize,
    log_new_vals: usize,
    start_index: usize,
    nonzero_index: usize,
    out: &mut [PE],
) -> Result<(), Error>
where
    P: PackedField,
    PE: PackedField<Scalar: ExtensionField<P::Scalar>>,