MDL-46088 Impossible to click on Atto in a Quiz in 'Secure' mode.
MDL-46088 Quiz: Prevent alert when clicking in editor in secure popup
MDL-46088 quiz secure window: further Atto JS fixes.
MDL-47183: viewhiddenactivities should use the module context

Thanks to Paulo Matos for the forum part of this change.
MDL-46712: Center EditPDF window on browser resize / zoom
MDL-47555 core_availability: Issue with page layout & grade restriction

* Set pagelayout before getting section info, otherwise conditional activity renderers will default to the default 'base' layout.
MDL-47499 tasks: Scheduled tasks custom schedule is reset on upgrade.

Add a unit test for reset_scheduled_tasks_for_component and make sure it doesn't clear
customised schedules for existing tasks.
MDL-47632 calendar: Fixed iCal link going blue after visiting it
MDL-30358 forms: strict validation is too strict
MDL-47704 Grades: Fix for set_usedinaggregation

Used in aggregation was not resetting previously set values
when recalculating an aggregation. This meant that items no longer
in the aggregation, were displayed with stale weights in the user report.
MDL-47738 gradereport_history: User selector handles broke with 0 user

It was impossible to reopen the dialogue when the last search result
did not return any user.
MDL-47684 mod: better validation of rating options
MDL-47752 grading: fixed bugs with the modgrade element
MDL-46499 navigation: better enrolled course limit

We now user $CFG->navcourselimit to limit the number of
courses shown in the navigation when browsing another users
full profile. Previously it showed all courses which caused
some slowdown.
MDL-47077 report_participation: fixed pagination in groups
MDL-47608 cachestore_mongo: fixed unit test error

If you configured your site to run mongo unit tests and had
the mongo extension and backend installed but did not have the
mongo service running you would get a fatal error when running
the unit tests.
That problem has been fixed by checking the mongo test instance
is ready before returning it.
MDL-46518 navigation: site glossaries now expand properly
MDL-47757 events: Fixed doc block and missing string.

The language events were missing the @since tag and
the grade single view report was missing a language
string.
MDL-47760 grades: dim category name if hidden
MDL-47675 phpunit: Update unit tests to pass on MSSQL

Unit tests were failing on MSSQL. gc_collect_cycles() was
removed from the phpunit utils.php file to save time in running
the tests, but MSSQL doesn't clean up open files as well as
other databases.

This patch includes the garbage collection for the unit tests
that require it.