Allow loading of factories from namespaced extensions

The previous glob did not allow there to be more than one level of
namespacing in the extension file structure. This change will support
extensions that have their factories in folder like
`lib/super_good/solidus_taxjar/testing_support/factories/*`.

Co-authored-by: Nick Van Doorn <nick@super.gd>

Author: forkata

lib/solidus_dev_support/testing_support/factories.rb

@@ -8,7 +8,7 @@ module TestingSupport
     module Factories
       def self.load_for(*engines)
         paths = engines.flat_map do |engine|
-          engine.root.glob('lib/*/testing_support/factories{,.rb}')
+          engine.root.glob('lib/**/testing_support/factories{,.rb}')
         end.map { |path| path.sub(/.rb\z/, '').to_s }
 
         FactoryBot.definition_file_paths = [