Cardano DB v2 restoration is missing `00000` immutables

## Why
The immutable files `00000` are not available when being restored by the Mithril client with the Cardano DB v2 certification. This causes the failure of the Cardano node at startup.

## What
Make the Cardano DB v2 certification fully support all the immutable files.

## How

- [x] Investigate the issue
- [x] Fix the issue