Migrate historical data between Chaingraph instances

[bitjson]

Chaingraph is designed to be easy to spin up and replace. Since most of Chaingraph's data is simply historical blockchain data, there's very little data in existing Chaingraph databases which can't be replicated by a new initial sync.

It would be valuable to develop an export/import method to preserve a normalized copy of the data which is not easily replaceable: node_transaction_history, node_block_history, any unconfirmed transactions, and any stale blocks. The export should not use any internal_ids (since these are not consistent from instance to instance), and the import script should be able to add the data from the export to an existing, synced Chaingraph instance.