SAK-50010 Rubrics: Reset criterion comments per student esp. for Grader

[hornersa]

Jira: https://sakaiproject.atlassian.net/browse/SAK-50010

There's an unfortunate downside with the proposed solution that I demo in a screencast attached to the jira linked above: a visible "glitching" that occurs anytime a criterion comment popover is opened. That said, the proposed fix should pass the test plan.

Note that as of this writing, I'll be away for about a week and a half (returning mid-July). In the meantime, please feel free to revise this PR with other commits to resolve this jira whose priority is Critical/Blocker. Nevertheless, I hope the proposed solution is at least in the right direction for getting this issue resolved soon.