roster: show activity columns based on "usage reports" permissions

fixes CNVS-13436

test plan:
  * for teachers, disable these permissions:
    * Add/remove other teachers, course designers or TAs to the course
    * Add/remove students for the course
  * enable View usage reports for the course
  * log in as a teacher
  * view the course roster
  * confirm that the activity columns are visible

Change-Id: Ida208431c5d94b5f6f3a7a2df2901e5c4300b3a0
Reviewed-on: https://gerrit.instructure.com/35891
Tested-by: Jenkins <jenkins@instructure.com>
Reviewed-by: Anthus Williams <awilliams@instructure.com>
QA-Review: August Thornton <august@instructure.com>
Product-Review: Braden Anderson <banderson@instructure.com>