DEV: Add memoization to reduce redis calls

lib/custom_wizard/custom_field.rb

@@ -140,7 +140,7 @@ class ::CustomWizard::CustomField
   end
 
   def self.cached_list
-    ::CustomWizard::Cache.wrap(LIST_CACHE_KEY) do
+    @cached_list ||= ::CustomWizard::Cache.wrap(LIST_CACHE_KEY) do
       PluginStoreRow.where(plugin_name: NAMESPACE).map do |record|
         create_from_store(record).as_json.with_indifferent_access
       end