Make prepareSynchronization overridable again

Closes gh-32000

Author: jhoeller

spring-tx/src/main/java/org/springframework/transaction/support/AbstractPlatformTransactionManager.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2023 the original author or authors.
+ * Copyright 2002-2024 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -571,7 +571,7 @@ private DefaultTransactionStatus newTransactionStatus(
 	/**
 	 * Initialize transaction synchronization as appropriate.
 	 */
-	private void prepareSynchronization(DefaultTransactionStatus status, TransactionDefinition definition) {
+	protected void prepareSynchronization(DefaultTransactionStatus status, TransactionDefinition definition) {
 		if (status.isNewSynchronization()) {
 			TransactionSynchronizationManager.setActualTransactionActive(status.hasTransaction());
 			TransactionSynchronizationManager.setCurrentTransactionIsolationLevel(