ZainoDB DbV1 refactor #862
Description
The DbV1 code (https://github.com/zingolabs/zaino/blob/dev/zaino-state/src/chain_index/finalised_state/db/v1.rs) is currently all in a single file which is very large, hindering development on this code. This module should be refactored into sub-modules, divided by capability.
This will require no code changes, just moving the current code into sub modules.
Documentation for this code should also be improved in the process to ease development further.