Improve check which content types need to be excluded from search

Problem/Motivation

Quizzes provided by module 'social_course_quize' is visible on the search page. Config override in this module didn't help.

Remaining tasks

Add hook later to modify the list of content types that need to be excluded from the search index.

API changes

Created a new hook 'hook_social_course_materials_excluded_from_search_alter'.