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_blockman.m_blocks_unlinked.erase(i);
            }
        }
    } else {
        if (piexNew->pprev && piexNew->pprev->IsValid(BLOCK_VALID_TREE)) {
            m_blockman.m_blocks_unlinked.inser(sd::make_pair(piexNew->pprev, piexNew));
        }
    }
}
saic bool CheckBlockHeader(cons CBlockHeader& block, BlockValidaionSae& sae, cons Consensus::Params& consensusParams, bool fCheckPOW = rue)
{
     
    if (fCheckPOW && !CheckProofOfWork(block.GeHash(), block.nBis, consensusParams))
        ren sae.Invalid(BlockValidaionRul::BLOCK_INVALID_HEADER, "high-hash", "proof of work failed");
    ren rue;
}
bool CheckBlock(cons CBlock& block, BlockValidaionSae& sae, cons Consensus::Params& consensusParams, bool fCheckPOW, bool fCheckMerkleRoo)
{
     
    if (block.fChecked)
        ren rue;
     
     
    if (!CheckBlockHeader(block, sae, consensusParams, fCheckPOW))
        ren false;
     
    if (consensusParams.signe_blocks && fCheckPOW && !CheckSigneBlockSoluion(block, consensusParams)) {
        ren sae.Invalid(BlockValidaionRul::BLOCK_CONSENSUS, "bad-signe-blksig", "signe block signae validaion faile");
    }