Feature/sections tool sm

This pull requests contains the following changes:

1. Add a pretty name in the lookup dictionary  for Test Student in the custom tag
2. Logic to delete  'Test Student' identified by 'StudentViewEnrollment' role, from the list of section enrollees.   
  Since this logic is reused in multiple places, moved to a separate utility which first invokes the backend API to fetch section enrollments and then applies a filter
3. Ensured that the enrollee count is also fixed in the section list logic
4. Unit cases for testing this utility