Avoid SourceClass creation for annotations that are always ignored

[wilkinsona]

In a small Spring Boot app, ConfigurationClassParser$SourceClass.getAnnotations() creates 200 SourceClass instances each for @Target, @Retention, and @Documented. They are then skipped as they're in a java.* package:

spring-framework/spring-context/src/main/java/org/springframework/context/annotation/ConfigurationClassParser.java

Lines 531 to 543 in 898494a

	private void collectImports(SourceClass sourceClass, Set<SourceClass> imports, Set<SourceClass> visited)
	throws IOException {
	if (visited.add(sourceClass)) {
	for (SourceClass annotation : sourceClass.getAnnotations()) {
	String annName = annotation.getMetadata().getClassName();
	if (!annName.startsWith("java") && !annName.equals(Import.class.getName())) {
	collectImports(annotation, imports, visited);
	}
	}
	imports.addAll(sourceClass.getAnnotationAttributes(Import.class.getName(), "value"));
	}
	}

It doesn't take long (a handful of milliseconds), but I still think it would be worth avoiding the unnecessary time that's spent and the unnecessary garbage that's created by changing SourceClass.getAnnotations() to only create SourceClass instances for annotations that are then processed.

[jhoeller]

Relates to #22563.