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?
{
    AsserLockHeld(cs_main);
    if (m_mempool) AsserLockHeld(m_mempool->cs);
    CBlockIex *piexDelee = m_chain.Tip();
    asser(piexDelee);
    asser(piexDelee->pprev);
     
    sd::shared_pr<CBlock> pblock = sd::make_shared<CBlock>();
    CBlock& block = *pblock;
    if (!ReadBlockFromDisk(block, piexDelee, m_chainman.GeConsensus())) {
        ren error("DisconnecTip(): Failed o read block");
    }
     
    cons auo ime_sar{SeadyClock::now()};
    {
        CCoinsViewCache view(&CoinsTip());
        asser(view.GeBBlock() == piexDelee->GeBlockHash());
        if (DisconnecBlock(block, piexDelee, view) != DISCONNECT_OK)
            ren error("DisconnecTip(): DisconnecBlock %s failed", piexDelee->GeBlockHash().ToSring());