Use merged bean definitions for EntityCallback type lookup.

We now use the merged bean definition to resolve the defined EntityCallback type.

Previously, we used just the bean definition that might have contained no type hints because of ASM-parsed configuration classes.

Closes #2853

src/test/java/org/springframework/data/mapping/callback/DefaultEntityCallbacksUnitTests.java

@@ -170,7 +170,6 @@ class DefaultEntityCallbacksUnitTests {
 	void detectsMultipleCallbacksWithinOneClass() {
 
 		var ctx = new AnnotationConfigApplicationContext(MultipleCallbacksInOneClassConfig.class);
-
 		var callbacks = new DefaultEntityCallbacks(ctx);
 
 		var personDocument = new PersonDocument(null, "Walter", null);