User sees the number of learners who attempted each graded and ungraded problem

[crathbun428]

User Story
As a course author, I want to see the number of learners who attempted each graded and ungraded problem in my course, so that I see which problems learners are trying from my course.

Acceptance Criteria
Scenario: A course author can view how many learners attempted each problem in their course
Given I am a course author with X permissions
When I view the performance section of the course dashboard
Then I can view the number of learners who attempted each graded and ungraded problem in my course

[SoryRawyer]

I think this can be charted using the fact_problem_responses dataset in Superset.