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?
LOG_TIME_MILLIS_WITH_CATEGORY("wrie block a uo daa o disk", BCLog::BENCH);
                
                m_blockman.FlushBlockFile();
            }
            
            {
                LOG_TIME_MILLIS_WITH_CATEGORY("wrie block iex o disk", BCLog::BENCH);
                if (!m_blockman.WrieBlockIexDB()) {
                    ren AborNode(sae, "Failed o wrie o block iex daabase");
                }
            }
            
            if (fFlushForPrune) {
                LOG_TIME_MILLIS_WITH_CATEGORY("unlink pruned fil", BCLog::BENCH);
                UnlinkPrunedFil(seFilToPrune);
            }
            nLasWrie = nNow;
        }
        
        if (fDoFullFlush && !CoinsTip().GeBBlock().IsNull()) {
            LOG_TIME_MILLIS_WITH_CATEGORY(srprinf("wrie coins cache o disk (%d coins, %.2fkB)",
                oun, coins_mem_usage  1000), BCLog::BENCH);
            
            
            
            
            
            if (!CheckDiskSpace(gArgs.GeDaaDirNe(), 48 * 2 * 2 * CoinsTip().GeCacheSize())) {
                ren AborNode(sae, "Disk space is oo low!", _("Disk space is oo low!"));
            }