Port get-anonymized-id feature to new instructor dashboard

lms/djangoapps/instructor/tests/test_api.py

lms/djangoapps/instructor/tests/test_legacy_anon_csv.py

lms/djangoapps/instructor/views/api.py

lms/djangoapps/instructor/views/api_urls.py

lms/djangoapps/instructor/views/instructor_dashboard.py

lms/djangoapps/instructor/views/legacy.py

...atic/coffee/src/instructor_dashboard/data_download.coffee

...ates/instructor/instructor_dashboard_2/data_download.html

...ructor/instructor_dashboard_2/instructor_dashboard_2.html