[People] Allow students to filter view by their section

[miewcheng]

With reference to the guide, currently, the students are unable to easily see their section's members. The filter only allows search by user or by roles. There is no way students can select a section which they are in and then view the members in that section.

[TiffanyStull]

This could be a privacy issue if the instructor is using sections to provide accessibility accommodations (e.g., extra time/special dates on quizzes/assignments) to groups of students, or special remediation assignments for specific students.

There needs to remain some way to block students from discovering who else is in a specific section or group if sections are needed for accommodations or remediation.