MDL-45982: Implement displaying of non error messages from a provider.
MDL-45381 mod_forum: changed event URL for subscription created/deleted events
MDL-46144 core_calendar: Fixed linking of labels on calendar pages
MDL-45381 mod_forum: updated unit tests for subscription created/deleted events
MDL-46225 core_admin: Changed heading to add a new user to a button
MDL-43849 mod_forum: Adding tests for observers
MDL-43849 enrol_meta: Renaming methods according to what they test
MDL-46212 question editing: extra answer fields notice.

It turns out that PHP does not interpret "$field[$key]" the way we were
expecting.
MDL-46212 questions: add {} whenver vars are put into "" strings

Having had one subtle bug cased be this, I decided to do a search and
fix all of these.
MDL-46208 cachestore_mongo: fixed invalid collection name use
MDL-42609 course: management page now selected default category initially
MDL-46016 auth_shibboleth: updated misleading comment

Also generated a random string for the password field in case it is ever used.
MDL-45945 mssql: force default database collation in all tables including temp table
MDL-45596 roles: Escape filter value before using it in form field
MDL-45678 assignsubmission_comments: Improve performance for permissions checking
MDL-46193 phpunit: Use random starting value on initialization.
MDL-46059 mod_lti: Changed LTI table column grade to an int.
MDL-45599 Remove string editingnoncorelangfile from core_admin

This string mentions 'add-on' and has been greylisted in AMOS since 2.0. The
usage of it was removed in 00b41d.
MDL-45599 Stop using the 'add-on' term

We now call them all as just 'plugins' for consistency. There where we need to
explicitly distinguish the source of the plugin, we say they are 'additional
plugins' on contrary to 'standards plugins' coming with the core.
MDL-46240 atto_collapse: fix icon url