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
state->pindexLastCommonBlock = LastCommonAncestor(state->pindexLastCommonBlock, state->pindexBestKnownBlock);
    if (state->pindexLastCommonBlock == state->pindexBestKnownBlock)
        return;
    std::vector<const CBlockIndex*> vToFetch;
    const CBlockIndex *pindexWalk = state->pindexLastCommonBlock;
    
    
    
    int nWindowEnd = state->pindexLastCommonBlock->nHeight + BLOCK_DOWNLOAD_WINDOW;
    int nMaxHeight = std::min<int>(state->pindexBestKnownBlock->nHeight, nWindowEnd + 1);
    NodeId waitingfor = -1;
    while (pindexWalk->nHeight < nMaxHeight) {
        
        
        
        int nToFetch = std::min(nMaxHeight - pindexWalk->nHeight, std::max<int>(count - vBlocks.size(), 128));
        vToFetch.resize(nToFetch);
        pindexWalk = state->pindexBestKnownBlock->GetAncestor(pindexWalk->nHeight + nToFetch);
        vToFetch[nToFetch - 1] = pindexWalk;
        for (unsigned int i = nToFetch - 1; i > 0; i--) {
            vToFetch[i - 1] = vToFetch[i]->pprev;
        }
        
        
        
        
        for (const CBlockIndex* pindex : vToFetch) {
            if (!pindex->IsValid(BLOCK_VALID_TREE)) {
                
                return;