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
LOCK(pto->cs_inventory);
            std::vector<CBlock> vHeaders;
            bool fRevertToInv = ((!state.fPreferHeaders &&
                                 (!state.fPreferHeaderAndIDs || pto->vBlockHashesToAnnounce.size() > 1)) ||
                                pto->vBlockHashesToAnnounce.size() > MAX_BLOCKS_TO_ANNOUNCE);
            const CBlockIndex *pBestIndex = nullptr; 
            ProcessBlockAvailability(pto->GetId()); 
            if (!fRevertToInv) {
                bool fFoundStartingHeader = false;
                
                
                
                for (const uint256 &hash : pto->vBlockHashesToAnnounce) {
                    const CBlockIndex* pindex = LookupBlockIndex(hash);
                    assert(pindex);
                    if (::ChainActive()[pindex->nHeight] != pindex) {
                        
                        fRevertToInv = true;
                        break;
                    }
                    if (pBestIndex != nullptr && pindex->pprev != pBestIndex) {