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.

When updating/deleting a section/module, the system now only
invalidate of the element (section/module), not the whole course cache
Also, the system now only recalculate the cache for element (section/module)
if necessary, not the whole course cache

Move module/section purging to course_modinfo:
  + course_modinfo::purge_course_section_cache_by_id was created to purge section by id
  + course_modinfo::purge_course_section_cache_by_number was created to purge section by number
  + course_modinfo::purge_course_module_cache was created to purge module

 - Introduce core_course_category::get_nearest_editable_subcategory()
 - This function will return the first creatable/manageable category
for current user
 - With this new function, we can fix the issue that the users with
course management or creation permision at category level cannot see
the manage menu on My courses page

Previously, the timeline block courses view included all courses in
alphabetical order, whether they contained any events matching the
relevant filters or not. This could be tedious and misleading if there
were many courses with no events appearing before a course which did
have matching events. Now, courses are only included if they contain
events matching the currently set time filter and search term. When
those values are modified, the block will be refreshed and fetch
results for the current values, and also takes these into
consideration when determining whether to display the show more courses
button.

Ferran Recio Calderó authored Jun 21, 2021 and Amaia committed Aug 20, 2021

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.

Until Moodle 4.0, renderer.php file was optional (although highly recommended)
for course formats. From Moodle 4.0 onwards, renderer is required to support
the new course editor implementation.
The legacy_format_renderer class has been created for backward compatibility,
to avoid some errors with course formats (such as social) without the renderer
file. Apart from that, course_format->get_renderer() method has been reviewed
to use this legacy_format_renderer when no renderer.php file is found.

This commit removes activity chooser user preference and
course preference page. Separate dropdowns to activity and
resource is also removed.

* activity_date_in_activity_should_contain_text()
  - Checks the presence of the given text in the activity's date info.
* activity_dates_information_in_activity_should_exist()
  - Checks the presence of activity dates information in the activity
    information output component.
* activity_dates_information_in_activity_should_not_exist()
  - Checks the absence of activity dates information in the activity
    information output component.

Deprecate \core_course_renderer::course_section_cm_completion(). It is
not being used anymore and is being replaced by
\core_renderer::activity_information().

For clients that wish to consume the original value of the custom
field (e.g. timestamps for date fields), rather than the formatted
version, add a new "valueraw" property to the returned data.

Under parallel development, when something is worth being commented
in upgrade.txt notes, it will be applied to all the development branches
using the "earliest" one to be released. So, if something changes
in 3.10 (and also is applied to master), the upgrade.txt notes will
show 3.10 in both branches.

Of course, if something only goes to one dev branch (say master), then the
master version will be used in the notes (4.0 in this case).

Padding nested course categories by space to make them render in a tree
structure does not really make a lot of sense as they are already being
rendered as full paths. It's simpler to show them without the
indentation.
Given this, there's not much point keeping make_categories_options().
So it's better to deprecate this function and call
core_course_category::make_categories_list() directly instead.

* moving course pattern generation to core_renderer

This is a refactor of the function to be able to get all the user
course groups in just one call