Deprecation of maxsection setting: MDL-84291

[PhMemmel]

The deprecation of the maxsections setting affects block_massaction. For example when duplicating into another course there is

Deprecation: core_courseformat\base::get_max_sections has been deprecated since 5.1. The maxsection setting is removed.. See MDL-84291 for more information.

    line 255 of /lib/classes/deprecation.php: call to debugging()
    line 136 of /lib/classes/deprecation.php: call to core\deprecation::emit_deprecation_notice()
    line 463 of /course/format/classes/base.php: call to core\deprecation::emit_deprecation_if_present()
    line 138 of /blocks/massaction/classes/form/section_select_form.php: call to core_courseformat\base->get_max_sections()
    line 217 of /lib/formslib.php: call to block_massaction\form\section_select_form->definition()
    line 174 of /blocks/massaction/action.php: call to moodleform->__construct()

There are for sure more places we have to fix that. The deprecation starts with Moodle 5.1. See https://moodle.atlassian.net/browse/MDL-84291

[Syxton]

This shouldn't be difficult to work around for a Moodle 5.1+ release. However I'm a little concerned about this part of the deprecation plan:

Flag the course max sections as deprecated and leave it only for third-party format plugins

So we will need to be able to check if the course format supports max_sections and check accordingly.