P2P: Additional info in handshake message

[heifner]

Current net_plugin protocol version: proto_savanna = 9.
Add new protocol version: proto_handshake_v2 = 10

handshake_message_v2 sent instead of handshake_message when handshake_message::network_version is >= proto_handshake_v2.

struct handshake_message_v2 : handshake_message {
   fc::time_point last_vote_received;  // report in connection status, allows node operators to see which connections have vote messages
   fc::time_point last_trx_received;  // report in connection status, allows node operators to see which connections have trxs
   block_num_type start_block = 0; // if block_log then what is the starting block, 0 if no block log
};

Current handshake_message

   struct handshake_message {
      uint16_t                   network_version = 0; ///< incremental value above a computed base
      chain_id_type              chain_id; ///< used to identify chain
      fc::sha256                 node_id; ///< used to identify peers and prevent self-connect
      chain::public_key_type     key; ///< authentication key; may be a producer or peer key, or empty
      int64_t                    time{0}; ///< time message created in nanoseconds from epoch
      fc::sha256                 token; ///< digest of time to prove we own the private key of the key above
      chain::signature_type      sig; ///< signature for the digest
      string                     p2p_address;
      uint32_t                   fork_db_root_num = 0;
      block_id_type              fork_db_root_id;
      uint32_t                   fork_db_head_num = 0;
      block_id_type              fork_db_head_id;
      string                     os;
      string                     agent;
      int16_t                    generation = 0;
   };

• On first handshake_message received when network_verison > proto_handshake_v2 send back a handshake_message_v2.
• Do not attempt sync from peer when start_block == 0 or needed block is < start_block.
• Add handshake_message_v2 info to connection status response.
• If configured as a block producer or finalizer, generate error log message if all peers do not have a last_vote_received and Savanna is active.