Issue #3433019 by andypost, catch: Replace deprecated help_topics module with obsolete stub

core/modules/help_topics/help_topics.info.yml

core/modules/help_topics/help_topics.module

.../help_topics/src/Controller/HelpTopicPluginController.php

core/modules/help_topics/src/HelpBreadcrumbBuilder.php

core/modules/help_topics/src/HelpSectionManager.php

core/modules/help_topics/src/HelpTopicDiscovery.php

core/modules/help_topics/src/HelpTopicPluginBase.php

core/modules/help_topics/src/HelpTopicPluginInterface.php

core/modules/help_topics/src/HelpTopicPluginManager.php

...dules/help_topics/src/HelpTopicPluginManagerInterface.php

core/modules/help_topics/src/HelpTopicTwig.php

core/modules/help_topics/src/HelpTopicTwigLoader.php

core/modules/help_topics/src/HelpTwigExtension.php

...s/help_topics/src/Plugin/HelpSection/HelpTopicSection.php

core/modules/help_topics/src/Plugin/Search/HelpSearch.php

core/modules/help_topics/src/SearchableHelpInterface.php

core/modules/help_topics/templates/help-topic.html.twig