Generate matching structure for configuration classes

This commit improves GeneratedClass to support inner classes, allowing
them to be registered by name with a type customizer, as
GeneratedClasses does for top level classes.

BeanDefinitionMethodGenerator leverages this feature to create a
matching structure for configuration classes that contain inner classes.

Closes gh-29213

spring-beans/src/testFixtures/java/org/springframework/beans/testfixture/beans/factory/aot/InnerBeanConfiguration.java

@@ -0,0 +1,40 @@
+/*
+ * Copyright 2002-2022 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.
+ * You may obtain a copy of the License at
+ *
+ *      https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.springframework.beans.testfixture.beans.factory.aot;
+
+/**
+ * A configuration with inner classes.
+ *
+ * @author Stephane Nicoll
+ */
+public class InnerBeanConfiguration {
+
+	public static class Simple {
+
+		public SimpleBean simpleBean() {
+			return new SimpleBean();
+		}
+
+		public static class Another {
+
+			public SimpleBean anotherBean() {
+				return new SimpleBean();
+			}
+
+		}
+	}
+}

spring-beans/src/testFixtures/java/org/springframework/beans/testfixture/beans/factory/aot/SimpleBeanConfiguration.java

@@ -17,6 +17,7 @@
 package org.springframework.beans.testfixture.beans.factory.aot;
 
 /**
+ * A sample configuration.
  *
  * @author Stephane Nicoll
  */