Implement a better MSM

[huitseeker]

solidity-verifier/src/blocks/grumpkin/Bn256.sol

Lines 76 to 87 in bf863c1

	function multiScalarMul(Bn256AffinePoint[] memory bases, uint256[] memory scalars)
	public
	returns (Bn256AffinePoint memory r)
	{
	require(scalars.length == bases.length, "MSM error: length does not match");
	r = scalarMul(bases[0], scalars[0]);
	for (uint256 i = 1; i < scalars.length; i++) {
	r = add(r, scalarMul(bases[i], scalars[i]));
	}
	}

This is a basic (correct but not super performant) MSM.

We can probably do better with e.g. :
https://github.com/zcash/halo2/blob/7df93fd855395dcdb301a857d4b33f37903bbf76/halo2_proofs/src/arithmetic.rs#L28-L116

[storojs72]

Got it now, thanks!