`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.
{
    int halvings = nHeight / consensusParams.nSubsidyHalvingInterval;
    
    if (halvings >= 64)
        return 0;
    CAmount nSubsidy = 50 * COIN;
    
    nSubsidy >>= halvings;
    return nSubsidy;
}
CoinsViews::CoinsViews(