feat: scoring for multistep ORA configuration

[mariajgrimaldi]

TL;DR - This PR implements behind a systems feature flag a grading strategy of accumulating scores obtained on each workflow step.

The changes I have made are intended to allow a grade that accumulates the final score of each step each time the grade changes. That is when the instructor grades the student, then the student's final grade is the sum of the steps graded so far (for now only staff). When the peers grade my submission, then the student's final grade is the sum of the steps graded so far (staff + peer). Thus, we do not modify how the score is calculated, but what the final score is.

What changed?

Now, the accumulative scoring strategy can be turned on/off system-wide. When off, the ORA scoring system works as usual.

Developer Checklist

• Reviewed the release process
• Translations and JS/SASS compiled
• Bumped version number in openassessment/__init__.py and package.json

Testing Instructions

1. Install this version into your environment.

2. Turn on the feature flag for the LMS:
   FEATURES['ENABLE_ACCUMULATIVE_GRADING'] = True

3. Configure your ORA with the default criteria

4. Configure the ORA steps as follows:
   

5. Now try replicating the following:

• As student1, I submit my essay.
• As student2, I submit my essay and grade student1's essay.
• As instructor, I grade student2's essay.
• As student2, I see my grade. If my instructor in criteria 1 gave me 5/5 and in criteria 2 gave me 1/5, I will have 6/10 and I will get a message indicating that I am waiting for a grade from my peers.
• As student1, I grade student2's essay.
• As student2, I check my grades. If the median of my peers gives 3/5 for criterion 1, and for criterion 2 is 4/5, then I will have:
  5 (median peer) + 5 (staff) = 10/10.
  3 (median peer) + 1 (staff) = 4/10
  And the total: 14/20
• As instructor, I grade student1's essay.
• As student1, I check my grade:
  3 (median peer) + 0 (staff) = 3/10.
  3 (median peer) + 1 (staff) = 4/10
  And the total: 7/20

Reviewer Checklist

Collectively, these should be completed by reviewers of this PR:

• I've done a visual code review
• I've tested the new functionality