`RewindBlockIndex` was made to allow nodes upgrading to new consensus rules post-segwit fork to 
download new consensus data (i.e witnesses) without having to go through a whole IBD. It has been pointed than now really few pre-segwit nodes care to upgrade and that this logic may be irrelevant.

See https://github.com/bitcoin/bitcoin/pull/17737#discussion_r358514335 in review  of #17737 for more context pointers.
CCoinsViewCache& view, const CChainParams& chainparams, bool fJustCheck = false) EXCLUSIVE_LOCKS_REQUIRED(cs_main);
    
    bool DisconnectTip(BlockValidationState& state, const CChainParams& chainparams, DisconnectedBlockTransactions* disconnectpool) EXCLUSIVE_LOCKS_REQUIRED(cs_main, m_mempool.cs);
    
    /** Mark a block as precious and reorganize.
     *
     * May not be called in a validationinterface callback.
     */
    bool PreciousBlock(BlockValidationState& state, const CChainParams& params, CBlockIndex* pindex) LOCKS_EXCLUDED(cs_main);
    
    bool InvalidateBlock(BlockValidationState& state, const CChainParams& chainparams, CBlockIndex* pindex) LOCKS_EXCLUDED(cs_main);
    
    void ResetBlockFailureFlags(CBlockIndex* pindex) EXCLUSIVE_LOCKS_REQUIRED(cs_main);
    
    bool ReplayBlocks(const CChainParams& params);
    bool RewindBlockIndex(const CChainParams& params) LOCKS_EXCLUDED(cs_main);
    
    bool LoadGenesisBlock(const CChainParams& chainparams);
    void PruneBlockIndexCandidates();
    void UnloadBlockIndex();
    
    bool IsInitialBlockDownload() const;
    /**
     * Make various assertions about the state of the block index.
     *
     * By default this only executes fully when using the Regtest chain; see: fCheckBlockIndex.
     */
    void CheckBlockIndex(const Consensus::Params& consensusParams);
    
    void LoadMempool(const ArgsManager& args);