[FEATURE] [MER-3504] one question at a time feature

[rgachuhi]

This PR adds a new attribute, “assessment_mode,” to the Revision and SectionResource schemas. This attribute will be an enum with the values “traditional” and “one_at_a_time.” Ensures that the relevant code for creating a new course section and applying publication updates to course sections copies these values from the underlying Revision to the corresponding SectionResource. Extends the Assessment Settings UX and Student Exceptions UX to allow Instructors to change these settings for a course section and for individual students

[rgachuhi]

Looks good. Though I noticed there is a wierd underscore happening in the selection text, maybe it is converting from an atom? Should we change so that this text reads with spaces instead of underscores?

Updated to remove underscores