Revert "PERF: Use 1 query to load group and tag notification default."

This reverts commit 5ef9d4d537.

The reverted commit caused issues, https://meta.discourse.org/t/there-are-no-visible-groups/163604. Reverting until further fixes can be put in place.

app/serializers/basic_group_serializer.rb

@@ -134,23 +134,11 @@ class BasicGroupSerializer < ApplicationSerializer
 
   [:watching, :regular, :tracking, :watching_first_post, :muted].each do |level|
     define_method("#{level}_category_ids") do
-      @group_category_notification_defaults ||= begin
-        GroupCategoryNotificationDefault.where(group: object).pluck(:category_id)
-      end
-
-      @group_category_notification_defaults.filter do |default|
-        default.notification_level == NotificationLevels.all[level]
-      end
+      GroupCategoryNotificationDefault.lookup(object, level).pluck(:category_id)
     end
 
     define_method("#{level}_tags") do
-      @group_tag_notification_defaults ||= begin
-        GroupTagNotificationDefault.where(group: object).joins(:tag).pluck('tags.name')
-      end
-
-      @group_tag_notification_defaults.filter do |default|
-        default.notification_level == NotificationLevels.all[level]
-      end
+      GroupTagNotificationDefault.lookup(object, level).joins(:tag).pluck('tags.name')
     end
   end