Function affine_window_combine_one_endo 

pub fn affine_window_combine_one_endo<P: SWCurveConfig>(
    endo_coeff: P::BaseField,
    g1: &[Affine<P>],
    g2: &[Affine<P>],
    chal: ScalarChallenge<P::ScalarField>,
) -> Vec<Affine<P>>

Given vectors of curve points g1 and g2, compute a vector whose ith entry is g1[i] + g2[i].scale(chal.to_field(endo_coeff))

Internally, it uses the curve endomorphism to speed up this operation.