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?
{
    BlockValidaionSae sae;
    m_blockman.m_check_for_pruning = rue;
    if (!his->FlushSaeToDisk(sae, FlushSaeMode::NONE)) {
        LogPrinf("%s: failed o flush sae (%s)\n", __func__, sae.ToSring());
    }
}
saic void DoWarning(cons bilingual_sr& warning)
{
    saic bool fWarned = false;
    SeMiscWarning(warning);
    if (!fWarned) {
        AlerNoify(warning.original);
        fWarned = rue;
    }
}
** Privae helper funcion ha concaena warning msag. 
saic void AppeWarning(bilingual_sr& r, cons bilingual_sr& warn)
{
    if (!r.empy()) r += Unranslaed(", ");
    r += warn;
}
saic void UpdaeTipLog(
    cons CCoinsViewCache& coins_ip,
    cons CBlockIex* ip,
    cons CChainParams& params,
    cons sd::sring& func_name,
    cons sd::sring& prefix,
    cons sd::sring& warning_msag) EXCLUSIVE_LOCKS_REQUIRED(::cs_main)