Added util method to retrieve individual course_run data from Catalog

lms/djangoapps/certificates/api.py

lms/djangoapps/certificates/models.py

lms/djangoapps/certificates/tests/test_webview_views.py

lms/djangoapps/certificates/views/webview.py

openedx/core/djangoapps/catalog/tests/factories.py

openedx/core/djangoapps/catalog/tests/test_utils.py

openedx/core/djangoapps/catalog/utils.py

openedx/core/lib/edx_api_utils.py