Support `ActionDispatch::SystemTestCase` within UrlHelpers compiler

[KaanOzkan]

ActionDispatch::SystemTestCase uses method_missing to utilize UrlHelpers https://github.com/rails/rails/blob/19e4b7a609e79b6be80b5355e4ff3882ad59f09e/actionpack/lib/action_dispatch/system_test_case.rb#L182.

We can add a special case within UrlHelpers compiler to mixin the generated modules:

class ActionDispatch::SystemTestCase
  include GeneratedPathHelpersModule
  include GeneratedUrlHelpersModule
end

[paracycle]

We already do this for ActionDispatch::IntegrationTest, I see no reason to not do it for ActionDispatch::SystemTestCase as well.