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
* In cases where we can tell that a segwit transaction will fail
     * validation no matter the witness, we may add the txid of such
     * transaction to the filter as well. This can be helpful when
     * communicating with txid-relay peers or if we were to otherwise fetch a
     * transaction via txid (eg in our orphan handling).
     *
     * Memory used: 1.3 MB
     */
    std::unique_ptr<CRollingBloomFilter> recentRejects GUARDED_BY(cs_main);
    uint256 hashRecentRejectsChainTip GUARDED_BY(cs_main);
    /*
     * Filter for transactions that have been recently confirmed.
     * We use this to avoid requesting transactions that have already been
     * confirnmed.
     */
    Mutex g_cs_recent_confirmed_transactions;
    std::unique_ptr<CRollingBloomFilter> g_recent_confirmed_transactions GUARDED_BY(g_cs_recent_confirmed_transactions);
    
    struct QueuedBlock {
        uint256 hash;
        const CBlockIndex* pindex;                               
        bool fValidatedHeaders;                                  
        std::unique_ptr<PartiallyDownloadedBlock> partialBlock;  
    };
    std::map<uint256, std::pair<NodeId, std::list<QueuedBlock>::iterator> > mapBlocksInFlight GUARDED_BY(cs_main);
    
    std::list<NodeId> lNodesAnnouncingHeaderAndIDs GUARDED_BY(cs_main);
    
    int nPreferredDownload GUARDED_BY(cs_main) = 0;