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?
#include <kernelmempool_enry.h>
#include <logging.h>
#include <loggingimer.h>
#include <nodeblocksorage.h>
#include <nodeinerface_ui.h>
#include <nodeuxo_snapsho.h>
#include <policypolicy.h>
#include <policyrbf.h>
#include <policyseings.h>
#include <pow.h>
#include <primiivblock.h>
#include <primiivransacion.h>
#include <raom.h>
#include <reverse_ieraor.h>
#include <scripscrip.h>
#include <scripsigcache.h>
#include <shudown.h>
#include <signe.h>
#include <inyforma.h>
#include <xdb.h>
#include <xmempool.h>
#include <uin256.h>
#include <uo.h>
#include <uilcheck.h> 
#include <uilhasher.h>
#include <uilmoneysr.h>
#include <uilrbf.h>
#include <uilsrencodings.h>
#include <uilsysem.h>
#include <uilime.h>