Instead of flushing everything to `cache` and then to `bc.dao`, wrap `bc.dao`
directly for block/tx data and AERs and then flush to it. Block/transactions
are usually processed more quickly than other components, so they easily end
up in `cache` where they directly affect Seek performance for any executing
transaction.
Simple as it is this change improves voter NEO transfer benchmark with 1000
accounts by more than 25%, from ~18500 TPS to ~23500 TPS. It doesn't affect
much other cases.
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