GRAILS-11116 Custom marshaller registrar bean does not work

This is the final attempt to fix this bug. This time instead of trying to change the logic of ConvertersConfigurationIntializer we ensure that initialization is done right after the given bean is initialized by the plugin. Previously it assumed that there wont be any marshaller registered before the initialize method is called in doWithDynamicMethods event hook.

All tests passed this time :)