Spring Add FullyQualifiedAnnotationBeanNameGenerator.INSTANCE

Spring 5.2.3 (b4c91e7dac91c6176a5412ed930d2c048cc5c42f) introduces the FullyQualifiedAnnotationBeanNameGenerator, but does not override/hide the static INSTANCE field from its parent, which seems confusing to me. Someone might access FullyQualifiedAnnotationBeanNameGenerator.INSTANCE and get a AnnotationBeanNameGenerator instead. Just like I did. 😅

This PR aims to solve that by adding a static INSTANCE field to FullyQualifiedAnnotationBeanNameGenerator, like its parent does too.

Comment From: evpaassen

Thanks for merging! :)