Custom data directory support for state snapshot

[Aniket21mathur]

Like geth there can be a --datadir flag using which the state of the local node can be stored and on restarting the service it can read the state from the custom directory, if it is passed, and continue on top of it.

[adarshsrivastava11]

Thanks @Aniket21mathur for pointing this out. In the background we're using Hardhat which intern uses ethereumjs/vm implementation to run a node. We're working on adding a DB layer. Will update shortly.