Evaluate batch-affine MSM circuit complexity

[zhenfeizhang]

We may be able to reduce constraint count for MSM a bit further.

https://hackmd.io/@tazAymRSQCGXTUKkbh1BAg/Sk27liTW9

https://github.com/Manta-Network/wasm-zkp-challenge/blob/optimized_pippenger/src/pippenger_msm.rs

https://github.com/arkworks-rs/algebra/issues/380, https://github.com/AztecProtocol/barretenberg/blob/f45c27ecd70a3c5607cf30ad5e36bcb4b7385b6d/barretenberg/src/aztec/ecc/curves/bn254/scalar_multiplication/scalar_multiplication.cpp#L114

Let's consider native computation. When we add a projective point with an affine point, we use mixed-addition formula and require 11 field multiplications. In batch affine, we add two vectors of affine points and require only 6 field multiplications and 0 division amortized for each point addition. This saves a lot and motivates us to use batch affine in MSM.

The improvement are not likely to hold for circuits, but it would be interesting to find out.