DEV: Added callback to change the query used to filter groups in search (#19884)

Added plugin registry that will allow adding callbacks that can change the query that is used
to filter groups while running a search.

lib/plugin/instance.rb

@@ -1292,6 +1292,10 @@ class Plugin::Instance
     DiscoursePluginRegistry.register_topic_preloader_association(fields, self)
   end
 
+  def register_search_group_query_callback(callback)
+    DiscoursePluginRegistry.register_search_groups_set_query_callback(callback, self)
+  end
+
   private
 
   def validate_directory_column_name(column_name)