Function build_withdraw_signing_bytes 

pub fn build_withdraw_signing_bytes(
    nonce: u64,
    chain_id: u64,
    to_discriminant: u64,
    to_address: &[u8; 32],
    asset_id: &[u8; 32],
    amount: u64,
) -> Vec<u8> 

Build the signing bytes for a withdrawal.

Layout: u64(nonce) + u64(chain_id) + u64(len(“withdraw”)) + “withdraw”

• u64(to_discriminant) + to_address(32)
• asset_id(32) + u64(amount)