Fix CDN_HOST not affected on full_asset_url (#18662)

* Fix CDN_HOST not affected to assets url

* Fix typo

app/helpers/routing_helper.rb

@@ -16,7 +16,11 @@ module RoutingHelper
   def full_asset_url(source, **options)
     source = ActionController::Base.helpers.asset_url(source, **options) unless use_storage?
 
-    URI.join(root_url, source).to_s
+    URI.join(asset_host, source).to_s
+  end
+
+  def asset_host
+    Rails.configuration.action_controller.asset_host || root_url
   end
 
   def full_pack_url(source, **options)