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.
if (fSendTrickle) {
                    LOCK(pto->m_tx_relay->cs_filter);
                    if (!pto->m_tx_relay->fRelayTxes) pto->m_tx_relay->setInventoryTxToSend.clear();
                }
                
                if (fSendTrickle && pto->m_tx_relay->fSendMempool) {
                    auto vtxinfo = m_mempool.infoAll();
                    pto->m_tx_relay->fSendMempool = false;
                    CFeeRate filterrate;
                    {
                        LOCK(pto->m_tx_relay->cs_feeFilter);
                        filterrate = CFeeRate(pto->m_tx_relay->minFeeFilter);
                    }
                    LOCK(pto->m_tx_relay->cs_filter);
                    for (const auto& txinfo : vtxinfo) {
                        const uint256& hash = state.m_wtxid_relay ? txinfo.tx->GetWitnessHash() : txinfo.tx->GetHash();
                        CInv inv(state.m_wtxid_relay ? MSG_WTX : MSG_TX, hash);
                        pto->m_tx_relay->setInventoryTxToSend.erase(hash);
                        
                        if (txinfo.fee < filterrate.GetFee(txinfo.vsize)) {
                            continue;
                        }
                        if (pto->m_tx_relay->pfilter) {
                            if (!pto->m_tx_relay->pfilter->IsRelevantAndUpdate(*txinfo.tx)) continue;
                        }
                        pto->m_tx_relay->filterInventoryKnown.insert(hash);
                        
                        vInv.push_back(inv);
                        if (vInv.size() == MAX_INV_SZ) {
                            m_connman.PushMessage(pto, msgMaker.Make(NetMsgType::INV, vInv));