JIRA: https://jira.spring.io/browse/INT-4181 * To avoid duplicate code move actual `Metrics` resolution to the `IntegrationManagementConfigurer` and delegate from the `IntegrationMBeanExporter` for backward compatibility * Minor refactoring and improvements in the `IntegrationMBeanExporter` * Fix typos in the `jms/AsyncGatewayTests` **Cherry-pick to 4.3.x**