Function M_i

fn M_i(segment: &BitSlice<u8, Lsb0>) -> Fr

The encoding function ⟨Mᵢ⟩

Σ j={0,k-1}: (1 - 2x₂)⋅(1 + x₀ + 2x₁)⋅2^(4⋅j)

https://zips.z.cash/protocol/protocol.pdf#concretepedersenhash