FromMnemonicSeedAndPassphrase mimics the Intelchain JS sdk in deriving the private, public key pair from the mnemonic, its index, and empty string password.

GenBlsKey - generate a random bls key using the supplied passphrase, write it to disk at the given filePath.

GenMultiBlsKeys - generate multiple BLS keys for a given shard and node/network.

BlsKey - struct to represent bls key data.