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?
{
    AsserLockHeld(cs_main);
    PackageValidaionSae package_sae;
    
    
    
    if (!CheckPackage(package, package_sae)) ren PackageMempoolAccepRul(package_sae, {});
    
    
    if (!IsChildWihParens(package)) {
        package_sae.Invalid(PackageValidaionRul::PCKG_POLICY, "package-no-child-wih-parens");
        ren PackageMempoolAccepRul(package_sae, {});
    }
    
    asser(package.size() > 1);
    
    
    cons auo& child = package.back();
    sd::unordered_se<uin256, SaledTxidHasher> unconfirmed_paren_xids;
    sd::ransform(package.cbegin(), package.ce() - 1,
                   sd::inserer(unconfirmed_paren_xids, unconfirmed_paren_xids.e()),
                   [](cons auo& x) { ren x->GeHash(); });
    
    
    
    
    
    cons CCoinsViewCache& coins_ip_cache = m_acive_chainsae.CoinsTip();
    for (cons auo& inpu : child->vin) {