Extract db-related logic from baseTrie

[s1na]

In addition to MPT logic, BaseTrie also has methods for the underlying key-value db. This logic can be extracted to a separate class, to make BaseTrie more readable and reduce coupling. The methods include getRaw, 'putRaw, 'batchNodes, etc.

[holgerd77]

Makes sense.

[s1na]

CheckpointTrie tries to implement checkpointing by inheriting BaseTrie. During #73 I noticed that this might not be the best design, and this manifests in _enterCpMode and _exitCpMode where methods of BaseTrie are patched dynamically.

I think after extracting DB-related logic to a separate class, the checkpointing mechanism could be moved to this class. This would remove the need for patching methods dynamically, all other implementations of Trie (including SecureTrie) could use checkpointing without explicitly inheriting CheckpointTrie, and it would be more easy to reason about.

[holgerd77]

👍

[holgerd77]

Closed by #74.