Merge branch 'MDL-55744-master_atto_should_not_autosave_on_not_loggedin_users' of https://github.com/dravek/moodle

Make sure that the autcomplete input field is wide enough to display the
placeholder text.

The form-autocomplete module uses three Mustache templates
core/form_autocomplete_input, core/form_autocomplete_suggestions and
core/form_autocomplete_selection. However, it did not support executing
the JS that is eventually part of those templates.

Before this patch, we only checked that the given provider has been
configured in the user or system preferences. However, if the provider's
component is disabled, it does not even appear in these preferences.
Additionally, there was no check that the message / notification
provider is among providers allowed to be consumed by the recipient.

The patch checks that the message origin is among providers returned by
the message_get_providers_for_user() so disabled plugins can't act as
sources of messages and users can't receive messages from providers they
do not have capability for. This mitigates the risk of abusing a plugin
as a source of spam, for example.

Unit test is fixed and extended. When the $CFG->messaging is disabled,
no messages between users should be sent (I can't understand why the
unit test was written in an opposite way). Added assertions for the
raised debugging message.

We were only exporting the one instance per item id.
Instead we should have been exporting all instances for each
item id.

Also rename course_in_list -> core_course_list_element
Deprecate class coursecat_sortable_records