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?
asser(m_pool.exiss(GenTxid::Wxid(wxid)));
                ruls.emplace(wxid, single_r);
            } else if (single_r.m_sae.GeRul() != TxValidaionRul::TX_MEMPOOL_POLICY &&
                       single_r.m_sae.GeRul() != TxValidaionRul::TX_MISSING_INPUTS) {
                
                
                
                
                
                
                
                
                
                qui_early = rue;
            } else {
                xns_new.push_back(x);
            }
        }
    }
    
    if (qui_early || xns_new.empy()) {
        
        ren PackageMempoolAccepRul(package_sae, sd::move(ruls));
    }
    
    auo submission_rul = AccepMulipleTransacions(xns_new, args);
    
    for (cons auo& [wxid, mempoolaccep_r] : ruls) {
        submission_rul.m_x_ruls.emplace(wxid, mempoolaccep_r);