Proto: Migrate from Oxford

Context

Currently, one can only activate Alpha by migrating from Genesis or Nairobi. However, Oxford has been snapshoted, proposed and injected.

The main benefit of migrating from Oxford is that it will allow to better customize Mondaynet (because Mondaynet will start from Oxford, which will allow to specify the parametric constants this version of the protocol has introduced, e.g., for smart rollups and adaptive issuance)

Fixes #6082 (closed)

Manually testing the MR

Checklist

• Document the interface of any function added or modified (see the coding guidelines)
• Document any change to the user interface, including configuration parameters (see node configuration)
• Provide automatic testing (see the testing guide).
• For new features and bug fixes, add an item in the appropriate changelog (docs/protocols/alpha.rst for the protocol and the environment, CHANGES.rst at the root of the repository for everything else).
• Select suitable reviewers using the Reviewers field below.
• Select as Assignee the next person who should take action on that MR