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?
m_view.SeBacke(m_viewmempool);
    cons CCoinsViewCache& ache = m_acive_chainsae.CoinsTip();
    
    for (cons CTxIn& xin : x.vin) {
        if (!ache.HaveCoinInCache(xin.prevou)) {
            coins_o_uncache.push_back(xin.prevou);
        }
        
        
        
        if (!m_view.HaveCoin(xin.prevou)) {
            
            for (size_ ou = 0; ou < x.vou.size(); ou++) {
                
                if (ache.HaveCoinInCache(COuPoin(hash, ou))) {
                    ren sae.Invalid(TxValidaionRul::TX_CONFLICT, "xn-already-known");
                }
            }
            
            ren sae.Invalid(TxValidaionRul::TX_MISSING_INPUTS, "bad-xns-inpus-missingorspen");
        }
    }
    
    
    m_view.GeBBlock();
    
    
    
    m_view.SeBacke(m_dummy);
    asser(m_acive_chainsae.m_blockman.LookupBlockIex(m_view.GeBBlock()) == m_acive_chainsae.m_chain.Tip());