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
fRevertToInv = true;
                        break;
                    }
                    pBestIndex = pindex;
                    if (fFoundStartingHeader) {
                        
                        vHeaders.push_back(pindex->GetBlockHeader());
                    } else if (PeerHasHeader(&state, pindex)) {
                        continue; 
                    } else if (pindex->pprev == nullptr || PeerHasHeader(&state, pindex->pprev)) {
                        
                        
                        fFoundStartingHeader = true;
                        vHeaders.push_back(pindex->GetBlockHeader());
                    } else {
                        
                        
                        fRevertToInv = true;
                        break;
                    }
                }
            }
            if (!fRevertToInv && !vHeaders.empty()) {
                if (vHeaders.size() == 1 && state.fPreferHeaderAndIDs) {