Revert "DEV: Add `add_controller_callback` server side plugin api."

This reverts commit 8233610d92.

Too much messy around with blocks to support `before_action` and
`around_action`.

lib/plugin/instance.rb

@@ -235,16 +235,6 @@ class Plugin::Instance
     end
   end
 
-  def add_controller_callback(klass_name, callback, &block)
-    reloadable_patch do |plugin|
-      klass = klass_name.to_s.classify.constantize rescue klass_name.to_s.constantize
-
-      klass.public_send(callback) do |controller, action|
-        block.call(controller, action) if plugin.enabled?
-      end
-    end
-  end
-
   # Add a post_custom_fields_whitelister block to the TopicView, respecting if the plugin is enabled
   def topic_view_post_custom_fields_whitelister(&block)
     reloadable_patch do |plugin|