Add FullyQualifiedAnnotationBeanNameGenerator.INSTANCE

Adds a static INSTANCE to FullyQualifiedAnnotationBeanNameGenerator,
just like its parent class, AnnotationBeanNameGenerator, does.

The class doesn't have any state and overriding/hiding the INSTANCE of
the superclass, this prevents unintended use of a regular
AnnotationBeanNameGenerator through
FullyQualifiedAnnotationBeanNameGenerator.INSTANCE.

spring-context/src/main/java/org/springframework/context/annotation/ConfigurationClassPostProcessor.java

@@ -99,7 +99,7 @@ public class ConfigurationClassPostProcessor implements BeanDefinitionRegistryPo
 	 * @see #setBeanNameGenerator
 	 */
 	public static final AnnotationBeanNameGenerator IMPORT_BEAN_NAME_GENERATOR =
-			new FullyQualifiedAnnotationBeanNameGenerator();
+			FullyQualifiedAnnotationBeanNameGenerator.INSTANCE;
 
 	private static final String IMPORT_REGISTRY_BEAN_NAME =
 			ConfigurationClassPostProcessor.class.getName() + ".importRegistry";

spring-context/src/main/java/org/springframework/context/annotation/FullyQualifiedAnnotationBeanNameGenerator.java

@@ -43,6 +43,14 @@ import org.springframework.util.Assert;
  */
 public class FullyQualifiedAnnotationBeanNameGenerator extends AnnotationBeanNameGenerator {
 
+	/**
+	 * A convenient constant for a default {@code FullyQualifiedAnnotationBeanNameGenerator} instance,
+	 * as used for configuration-level import purposes.
+	 */
+	public static final FullyQualifiedAnnotationBeanNameGenerator INSTANCE =
+			new FullyQualifiedAnnotationBeanNameGenerator();
+
+
 	@Override
 	protected String buildDefaultBeanName(BeanDefinition definition) {
 		String beanClassName = definition.getBeanClassName();