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
headers[0].GetHash().ToString(),
                    headers[0].hashPrevBlock.ToString(),
                    pindexBestHeader->nHeight,
                    pfrom.GetId(), nodestate->nUnconnectingHeaders);
            
            
            
            UpdateBlockAvailability(pfrom.GetId(), headers.back().GetHash());
            if (nodestate->nUnconnectingHeaders % MAX_UNCONNECTING_HEADERS == 0) {
                Misbehaving(pfrom.GetId(), 20, strprintf("%d non-connecting headers", nodestate->nUnconnectingHeaders));
            }
            return;
        }
        uint256 hashLastBlock;
        for (const CBlockHeader& header : headers) {
            if (!hashLastBlock.IsNull() && header.hashPrevBlock != hashLastBlock) {
                Misbehaving(pfrom.GetId(), 20, "non-continuous headers sequence");
                return;
            }
            hashLastBlock = header.GetHash();
        }
        
        
        if (!LookupBlockIndex(hashLastBlock)) {
            received_new_header = true;
        }
    }
    BlockValidationState state;
    if (!m_chainman.ProcessNewBlockHeaders(headers, state, m_chainparams, &pindexLast)) {
        if (state.IsInvalid()) {