MDL-43044 events: Add a course_module_instance_list_viewed abstract class
MDL-43044 events: Deprecate course_module_instances_list_viewed abstract class
MDL-43044 events: Deprecate and remove code duplication from instances_list_viewed events
MDL-43044 events: Add unit tests
MDL-40920 mod_url: replaced add_to_log calls with events