AFAICT, as of commit a0a422c,  we have 2 different logics to evict outbound peers : lagging-chain (`ConsiderEviction`) and (`CheckForStaleTipAndEvictPeers`). The former to sanitize out lazy/buggy peers who have never sent us a valid header and are always staying behind our tip, the latter triggered in case of stale tip due to block variance to seek a better chain by rotating our outbound peers if we already reach an outbound limit (`EvictExtraOutboundPeers`).

Block-relay-only peers were introduced by #15719. Contrary to outbound full-relay peers who provided us at least a useful header, they're not protected by lagging-chain eviction.

We actually have a comment inside `ProcessHeadersMessage` indicating the contrary behavior. We should either document cleanly that block-relay-only aren't protected or effectively extend the scope of protection to them.

Hinted during #19724 review, see https://github.com/bitcoin/bitcoin/pull/19724#discussion_r475144532
{
    
    
    
    uint64_t hashAddr = addr.GetHash();
    const CSipHasher hasher = connman.GetDeterministicRandomizer(RANDOMIZER_ID_ADDRESS_RELAY).Write(hashAddr << 32).Write((GetTime() + hashAddr) / (24 * 60 * 60));
    FastRandomContext insecure_rand;
    
    unsigned int nRelayNodes = (fReachable || (hasher.Finalize() & 1)) ? 2 : 1;
    std::array<std::pair<uint64_t, CNode*>,2> best{{{0, nullptr}, {0, nullptr}}};
    assert(nRelayNodes <= best.size());
    auto sortfunc = [&best, &hasher, nRelayNodes](CNode* pnode) {
        if (pnode->RelayAddrsWithConn()) {
            uint64_t hashKey = CSipHasher(hasher).Write(pnode->GetId()).Finalize();
            for (unsigned int i = 0; i < nRelayNodes; i++) {
                 if (hashKey > best[i].first) {
                     std::copy(best.begin() + i, best.begin() + nRelayNodes - 1, best.begin() + i + 1);
                     best[i] = std::make_pair(hashKey, pnode);
                     break;
                 }
            }
        }
    };
    auto pushfunc = [&addr, &best, nRelayNodes, &insecure_rand] {
        for (unsigned int i = 0; i < nRelayNodes && best[i].first != 0; i++) {
            best[i].second->PushAddress(addr, insecure_rand);
        }
    };
    connman.ForEachNodeThen(std::move(sortfunc), std::move(pushfunc));