The further discussion about after implementation of BLS

[colibrishin]

• There is an ongoing discussion of forbidding zero value private key and public key (See Infinity pubkey and signature supranational/blst#11) due to the soundness and producing the infinite public key and signature. For now, This is allowed for the sake of standardization (IETF standard has no mention of blocking neither zero-value private key nor public key.)

• The behavior of the Infinite Public key and Signature should be further investigated. For more details, See also Security of BLS batch verification.

• The Proof of Possession is for validating whether the public key is not aggregated and proving there is a pair of private key. It should be enough checking once and that moment is when the non-validator peer is trying to bonding as a validator.

• The byte size of Vote and LastCommit will be increases after the replacement of Public Key and Signature to BLS.

• This PR does not cover ProtectedPrivateKey, Web3KeyStore, Address and AddressExtensions modification. (https://eips.ethereum.org/EIPS/eip-2335)