Fix #262 distance oracle pool index

• Fixed #262 (closed): Switched to continuous indexing for naming distance evaluation files to prevent old files from being picked up by the inherent, avoiding unexpected behavior.
• Added crate-level documentation to provide an overview of the distance oracle's purpose and usage.
• Added a landing page for documentation duniter/index.html.
• Added a prefix check to prevent mismatches between the oracle and runtime versions, avoiding the Smith being penalized for a negligence error.
• Added log for distance-oracle started from the main binary.
• Refactored run and run_and_save oracle main functions:
  • Split into three thematic functions for better modularity:
    1. Checks if there is work to do and ensures files can be saved successfully.
    2. Handles the distance evaluation logic.
    3. Saves the computed distance to a file and cleans up outdated files.