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.
CConnman& connman)
{
    uint8_t filter_type_ser;
    uint256 stop_hash;
    vRecv >> filter_type_ser >> stop_hash;
    const BlockFilterType filter_type = static_cast<BlockFilterType>(filter_type_ser);
    const CBlockIndex* stop_index;
    BlockFilterIndex* filter_index;
    if (!PrepareBlockFilterRequest(peer, chain_params, filter_type, 0, stop_hash,
                                   std::numeric_limits<uint32_t>::max(),
                                   stop_index, filter_index)) {
        return;
    }
    std::vector<uint256> headers(stop_index->nHeight / CFCHECKPT_INTERVAL);
    
    const CBlockIndex* block_index = stop_index;