For every peer expose through `getpeerinfo` RPC whether or not we selected them as HB peers, and whether or not they selected us as HB peers.

Suggestion by @gmaxwell.
{
    size_t nMessageSize = msg.data.size();
    LogPrint(BCLog::NET, "sending %s (%d bytes) peer=%d\n",  SanitizeString(msg.m_type), nMessageSize, pnode->GetId());
    
    std::vector<unsigned char> serializedHeader;
    pnode->m_serializer->prepareForTransport(msg, serializedHeader);
    size_t nTotalSize = nMessageSize + serializedHeader.size();
    size_t nBytesSent = 0;
    {
        LOCK(pnode->cs_vSend);
        bool optimisticSend(pnode->vSendMsg.empty());
        
        pnode->mapSendBytesPerMsgCmd[msg.m_type] += nTotalSize;
        pnode->nSendSize += nTotalSize;
        if (pnode->nSendSize > nSendBufferMaxSize)
            pnode->fPauseSend = true;
        pnode->vSendMsg.push_back(std::move(serializedHeader));
        if (nMessageSize)
            pnode->vSendMsg.push_back(std::move(msg.data));
        
        if (optimisticSend == true)
            nBytesSent = SocketSendData(pnode);
    }
    if (nBytesSent)
        RecordBytesSent(nBytesSent);
}
bool CConnman::ForNode(NodeId id, std::function<bool(CNode* pnode)> func)