Optimize ClassNameReader.getClassName via direct ASM API

getClassName now calls ClassReader.getClassName() directly instead
of routing through the visitor-based getClassInfo. Previously, it
allocated a List and a ClassVisitor and decoded super_class and
every interface name only to discard all but the first element.

The method is on the hot path of every CGLIB proxy class definition,
so this change significantly lowers its per-call processing cost.

Closes gh-36814

Signed-off-by: cookie-meringue <daehyeon3351@gmail.com>

spring-core/src/main/java/org/springframework/cglib/core/ClassNameReader.java

@@ -34,9 +34,11 @@ public class ClassNameReader {
 	private static class EarlyExitException extends RuntimeException {
 	}
 
+	// SPRING PATCH BEGIN
 	public static String getClassName(ClassReader r) {
-		return getClassInfo(r)[0];
+		return r.getClassName().replace('/', '.');
 	}
+	// SPRING PATCH END
 
     public static String[] getClassInfo(ClassReader r) {
         final List<String> array = new ArrayList<>();