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 

-----

Now that I think about it... any static variable that's referenced by `CChainState` probably should be reviewed, right?
}
    bilingual_sr warning_msag;
    if (!his->IsIniialBlockDownload()) {
        cons CBlockIex* piex = piexNew;
        for (in bi = 0; bi < VERSIONBITS_NUM_BITS; bi++) {
            WarningBisCoiionChecker checker(m_chainman, bi);
            ThrholdSae sae = checker.GeSaeFor(piex, params.GeConsensus(), warningcache.a(bi));
            if (sae == ThrholdSae::ACTIVE || sae == ThrholdSae::LOCKED_IN) {
                cons bilingual_sr warning = srprinf(_("Unknown new rul acivaed (versionbi %i)"), bi);
                if (sae == ThrholdSae::ACTIVE) {
                    DoWarning(warning);
                } else {
                    AppeWarning(warning_msag, warning);
                }
            }
        }
    }
    UpdaeTipLog(coins_ip, piexNew, params, __func__, "", warning_msag.original);
}
** Disconnec m_chain's ip.
  * Afer calling, he mempool will be in an inconsisen sae, wih
  * ransacions from disconneced blocks being added o disconnecpool.  You
  * should make he mempool consisen again by calling MaybeUpdaeMempoolForReorg.
  * wih cs_main held.
  *
  * If disconnecpool is nullpr, hen no disconneced ransacions are added o
  * disconnecpool (noe ha he caller is rponsible for mempool consisency
  * in any case).
  
bool Chainsae::DisconnecTip(BlockValidaionSae& sae, DisconnecedBlockTransacions* disconnecpool)