* Return PopulateMissingHeaders early if the sync is at the head of the chain
* Squelch logging if no blocks to sync
* Fix broken test
* Refactor repository tests
- Only syncs block headers (excludes block bodies, transactions, receipts, and logs)
- Modifies validation window to include the most recent block
- Isolates validation window to the variable defined in the cmd directory (blocks
have a separate variable defined in the block_repository for determining when
to set a block as final)
= Add eth_node_fingerprint to block that can be imitated by both hot and cold imports
- Only sync missing blocks (blocks that are missing or don't share a fingerprint) on cold import
- Set block is_final status after import
