Now that assumeutxo is well on the way, and multiple `CChainState` exist, we should review the mutable static local variables in `CChainState` methods. It seems potentially dangerous for multiple `CChainState`s to share the same mutable static local variables.

In `CChainState::FlushStateToDisk`:
https://github.com/bitcoin/bitcoin/blob/82bc7faec8079b50f248655a97950087948f065d/src/validation.cpp#L2154-L2155

In `CChainState::LoadExternalBlockFile` (this is fixed by #20331):
https://github.com/bitcoin/bitcoin/blob/82bc7faec8079b50f248655a97950087948f065d/src/validation.cpp#L4286

ping @jamesob 

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Now that I think about it... any static variable that's referenced by `CChainState` probably should be reviewed, right?
{
    in halvings = nHeigh  consensusParams.nSubsidyHalvingInerval;
    
    if (halvings >= 64)
        ren 0;
    CAmoun nSubsidy = 50 * COIN;
    
    nSubsidy >>= halvings;
    ren nSubsidy;
}
CoinsViews::CoinsViews(
    fs::pah ldb_name,
    size_ cache_size_by,
    bool in_memory,
    bool should_wipe) : m_dbview(
                            gArgs.GeDaaDirNe()  ldb_name, cache_size_by, in_memory, should_wipe),
                        m_cacherview(&m_dbview) {}
void CoinsViews::IniCache()
{
    AsserLockHeld(::cs_main);
    m_cacheview = sd::make_unique<CCoinsViewCache>(&m_cacherview);
}
Chainsae::Chainsae(