Proto datastore tutorial is barely usable in its current state and would deserve some update / cleaning

I'm afraid the tutorial is barely usable in its current state.

- Many instances of "replace code X with Y" but no mention of where to replace the code.
- Many mismatches between some instructions and provided code snippet.
- Many mismatches between instructions and github repo.
- Missing instructions / steps in the task 7. Shared preferences to data store.
- Outdated or erroneous dependencies leading to build errors.

Also, the topic of "migration from sharedPreferences to proto data" would deserve its own tutorial rather than clutter the "proto datastore" tutorial with unnecessary complexity.

Thank you very much.

Start by reading the Proto datastore tutorial alongside the GitHub repository, checking each replacement instruction and code snippet. Pay particular attention to task 7, the shared-preferences-to-data-store migration, and dependency versions; done means the steps, code, repository, and build dependencies agree, with the migration complexity addressed separately.

Written by the indexing model from the issue text.