`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.
return m_coins_views && m_coins_views->m_cacheview;
    }
    
    
    CChain m_chain;
    /**
     * The blockhash which is the base of the snapshot this chainstate was created from.
     *
     * IsNull() if this chainstate was not created from a snapshot.
     */
    const uint256 m_from_snapshot_blockhash{};
    /**
     * The set of all CBlockIndex entries with BLOCK_VALID_TRANSACTIONS (for itself and all ancestors) and
     * as good as our current tip or better. Entries may be failed, though, and pruning nodes may be
     * missing the data for the block.
     */
    std::set<CBlockIndex*, CBlockIndexWorkComparator> setBlockIndexCandidates;
    
    CCoinsViewCache& CoinsTip() EXCLUSIVE_LOCKS_REQUIRED(cs_main)