Replace Configuration fully qualified name by constant

See gh-42311

Author: mushroom528

spring-boot-project/spring-boot-tools/spring-boot-configuration-processor/src/main/java/org/springframework/boot/configurationprocessor/ConfigurationMetadataAnnotationProcessor.java

@@ -69,7 +69,7 @@
 		ConfigurationMetadataAnnotationProcessor.REST_CONTROLLER_ENDPOINT_ANNOTATION,
 		ConfigurationMetadataAnnotationProcessor.SERVLET_ENDPOINT_ANNOTATION,
 		ConfigurationMetadataAnnotationProcessor.WEB_ENDPOINT_ANNOTATION,
-		"org.springframework.context.annotation.Configuration" })
+		ConfigurationMetadataAnnotationProcessor.CONFIGURATION_ANNOTATION })
 public class ConfigurationMetadataAnnotationProcessor extends AbstractProcessor {
 
 	static final String ADDITIONAL_METADATA_LOCATIONS_OPTION = "org.springframework.boot.configurationprocessor.additionalMetadataLocations";
@@ -104,6 +104,8 @@ public class ConfigurationMetadataAnnotationProcessor extends AbstractProcessor
 
 	static final String AUTO_CONFIGURATION_ANNOTATION = "org.springframework.boot.autoconfigure.AutoConfiguration";
 
+	static final String CONFIGURATION_ANNOTATION = "org.springframework.context.annotation.Configuration";
+
 	private static final Set<String> SUPPORTED_OPTIONS = Collections
 		.unmodifiableSet(Collections.singleton(ADDITIONAL_METADATA_LOCATIONS_OPTION));