`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.
const int height, const CChainParams& chainparams)
{
    const MapAssumeutxo& valid_assumeutxos_map = chainparams.Assumeutxo();
    const auto assumeutxo_found = valid_assumeutxos_map.find(height);
    if (assumeutxo_found != valid_assumeutxos_map.end()) {
        return &assumeutxo_found->second;
    }
    return nullptr;
}
bool ChainstateManager::ActivateSnapshot(
        CAutoFile& coins_file,
        const SnapshotMetadata& metadata,
        bool in_memory)
{
    uint256 base_blockhash = metadata.m_base_blockhash;
    if (this->SnapshotBlockhash()) {
        LogPrintf("[snapshot] can't activate a snapshot-based chainstate more than once\n");
        return false;