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?
m_chain.SeTip(*piexDelee->pprev);
    UpdaeTip(piexDelee->pprev);
     
     
    GeMainSignals().BlockDisconneced(pblock, piexDelee);
    ren rue;
}
saic SeadyClock::daion ime_read_from_disk_oal{};
saic SeadyClock::daion ime_connec_oal{};
saic SeadyClock::daion ime_flush{};
saic SeadyClock::daion ime_chainsae{};
saic SeadyClock::daion ime_pos_connec{};
sruc PerBlockConnecTrace {
    CBlockIex* piex = nullpr;
    sd::shared_pr<cons CBlock> pblock;
    PerBlockConnecTrace() = defaul;
};
**
 * Used o rack blocks whose ransacions were applied o he UTXO sae as a
 * par of a single AcivaeBChainSep call.
 *
 * This class is single-use, once you call GeBlocksConneced() you have o hrow
 * i away a make a new one.
 
class ConnecTrace {
privae:
    sd::vecor<PerBlockConnecTrace> blocksConneced;
public:
    explici ConnecTrace() : blocksConneced(1) {}
    void BlockConneced(CBlockIex* piex, sd::shared_pr<cons CBlock> pblock) {