Feature: Expose more easily last the two versions of a saved exercise

[erikmd]

Related issue(s) or PR(s): N/A

Related project scope(s): UI, learn-ocaml-client, Teacher-dashboard

Related user(s): @erikmd

The problem

Currently, the webapp views (student UI vs. teacher dashboard) only show one flavor of the "last version of the exercise":

• the last contents of save.json/exercises-editors for the student UI
• the last version of the graded exercise for the teacher dashboard

Additionally it is feasible for student to also retrieve the last version of the graded exercises by clicking on Download all source files in the home page. But it is certainly not very user-friendly.

Wanted solution

• In the student UI:
  • Replace the Reset button and icon with a drop-down button that proposes:
    • Reset to template
    • Reset to last graded version
    • Reset to last saved draft
• In the teacher dashboard:
  • Add another tab Draft after Answer that displays the last saved draft (although it is not taken into account for the grading; maybe add a tooltip in the Draft tab to remind this)
• In learn-ocaml-client:
  • Double-check what learn-ocaml-client fetch fetches
  • Provide a similar command, e.g., learn-ocaml-client fetch-graded, to fetch the last graded version

Remarks to be aware when reviewing this feature:

• Check that in the student UI, when resetting the editor with one of the 3 choices, the exercise is not automatically synced yet.
• Check what happens w.r.t. the refresh of the teacher dashboard when an exercise has been very recently synced/graded → open a new issue if need be.
• TODO internationalization with @erikmd

Considered alternatives

N/A

Additional context

N/A