Improve mapping function in ExtendedEntityManagerCreator.createProxy()

Closes gh-27456

Author: stsypanov

spring-orm/src/main/java/org/springframework/orm/jpa/ExtendedEntityManagerCreator.java

@@ -230,10 +230,10 @@ private static EntityManager createProxy(
 
 		if (emIfc != null) {
 			interfaces = cachedEntityManagerInterfaces.computeIfAbsent(emIfc, key -> {
-				Set<Class<?>> ifcs = new LinkedHashSet<>(4);
-				ifcs.add(key);
-				ifcs.add(EntityManagerProxy.class);
-				return ClassUtils.toClassArray(ifcs);
+				if (EntityManagerProxy.class.equals(key)) {
+					return new Class<?>[] {key};
+				}
+				return new Class<?>[] {key, EntityManagerProxy.class};
 			});
 		}
 		else {