To ensure legacy course formats works on Moodle 4.0 some method are
reintroduced (but marked as deprecated) like start_section_list and
end_section_list. Furthermore, the course_section_cm_availability
returns a string again as expected.
For legacy reasons, the course renderings uses a format setting to know
if the page is multiple sections per page or a single section per page.
This format specific dependency is not solved using a get_course_display
format method any plugin can extend.
Move the section visible logic to the format base class. This way format
plugins can decide whenever a section is visible or not instead of using
format custom settings from core.
The course index is the first UI component that implements the new
drawers and the reactive components. The course index uses the course
state to present the current course structure and changes whenever
that structure change.