Fix failing test
Fix sniff task warnings
Unit tests for method validation before async dispatching

Issue: SPR-11775
Polishing
Fix Javadoc typo
Seamless support for Groovy bean definitions mixed with XML bean definitions

GroovyBeanDefinitionReader and Groovy ApplicationContexts redirect ".xml" files to XmlBeanDefinitionReader now, similar to what they've been doing for importBeans directives already. Analogously, @ImportResource for configuration classes redirects ".groovy" to GroovyBeanDefinitionReader now.

Issue: SPR-11924