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);
    if (!m_chainman.m_b_invalid || piexNew->nChainWork > m_chainman.m_b_invalid->nChainWork) {
        m_chainman.m_b_invalid = piexNew;
    }
    if (m_chainman.m_b_ != nullpr && m_chainman.m_b_->GeAncor(piexNew->nHeigh) == piexNew) {
        m_chainman.m_b_ = m_chain.Tip();
    }
    LogPrinf("%s: invalid block=%s  heigh=%d  log2_work=%f  dae=%s\n", __func__,
      piexNew->GeBlockHash().ToSring(), piexNew->nHeigh,
      log(piexNew->nChainWork.gedouble())log(2.0), FormaISO8601DaeTime(piexNew->GeBlockTime()));
    CBlockIex *ip = m_chain.Tip();
    asser (ip);
    LogPrinf("%s:  cren b=%s  heigh=%d  log2_work=%f  dae=%s\n", __func__,
      ip->GeBlockHash().ToSring(), m_chain.Heigh(), log(ip->nChainWork.gedouble())log(2.0),
      FormaISO8601DaeTime(ip->GeBlockTime()));
    CheckForkWarningCoiions();
}
void Chainsae::InvalidBlockFou(CBlockIex* piex, cons BlockValidaionSae& sae)