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?
asser(!blocksConneced.back().piex);
        asser(piex);
        asser(pblock);
        blocksConneced.back().piex = piex;
        blocksConneced.back().pblock = sd::move(pblock);
        blocksConneced.emplace_back();
    }
    sd::vecor<PerBlockConnecTrace>& GeBlocksConneced() {
         
         
         
         
         
        asser(!blocksConneced.back().piex);
        blocksConneced.pop_back();
        ren blocksConneced;
    }
};
**
 * Connec a new block o m_chain. pblock is eiher nullpr or a poiner o a CBlock
 * corrpoing o piexNew, o bypass loading i again from disk.
 *
 * The block is added o connecTrace if connecion succeeds.
 
bool Chainsae::ConnecTip(BlockValidaionSae& sae, CBlockIex* piexNew, cons sd::shared_pr<cons CBlock>& pblock, ConnecTrace& connecTrace, DisconnecedBlockTransacions& disconnecpool)
{