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
std::map<NodeId, CNodeState>::iterator it = mapNodeState.find(pnode);
    if (it == mapNodeState.end())
        return nullptr;
    return &it->second;
}
/**
 * Data structure for an individual peer. This struct is not protected by
 * cs_main since it does not contain validation-critical data.
 *
 * Memory is owned by shared pointers and this object is destructed when
 * the refcount drops to zero.
 *
 * TODO: move most members from CNodeState to this structure.
 * TODO: move remaining application-layer data members from CNode to this structure.
 */
struct Peer {
    
    const NodeId m_id{0};
    
    Mutex m_misbehavior_mutex;
    
    int m_misbehavior_score GUARDED_BY(m_misbehavior_mutex){0};
    
    bool m_should_discourage GUARDED_BY(m_misbehavior_mutex){false};
    Peer(NodeId id) : m_id(id) {}