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.
m_connman.PushMessage(pto, msgMaker.Make(NetMsgType::HEADERS, vHeaders));
                    state.pindexBestHeaderSent = pBestIndex;
                } else
                    fRevertToInv = true;
            }
            if (fRevertToInv) {
                
                
                
                if (!pto->vBlockHashesToAnnounce.empty()) {
                    const uint256 &hashToAnnounce = pto->vBlockHashesToAnnounce.back();
                    const CBlockIndex* pindex = LookupBlockIndex(hashToAnnounce);
                    assert(pindex);
                    
                    
                    
                    if (::ChainActive()[pindex->nHeight] != pindex) {
                        LogPrint(BCLog::NET, "Announcing block %s not on main chain (tip=%s)\n",
                            hashToAnnounce.ToString(), ::ChainActive().Tip()->GetBlockHash().ToString());
                    }
                    
                    if (!PeerHasHeader(&state, pindex)) {
                        pto->vInventoryBlockToSend.push_back(hashToAnnounce);
                        LogPrint(BCLog::NET, "%s: sending inv peer=%d hash=%s\n", __func__,
                            pto->GetId(), hashToAnnounce.ToString());
                    }
                }
            }
            pto->vBlockHashesToAnnounce.clear();
        }