Changes to GET `/api/v0/main-frontend/exercise-slide-submissions/{submission_id}/info"`- Returns data necessary for rendering a submission.

added the optional property tasks/items/previous_submission/oneOf[#/components/schemas/ExerciseTaskSubmission]/data_files to the response with the 200 status

added the required property tasks/items/previous_submission/oneOf[#/components/schemas/ExerciseTaskSubmission]/answer_kind to the response with the 200 status

added the new NotAnsweredAndLocked enum value to the user_exercise_state/oneOf[#/components/schemas/UserExerciseState]/reviewing_stage response property for the response status 200