Add support for ImportAware callback

This commit adds a way for a BeanFactoryPostProcessor to participate to
AOT optimizations by contributing code that replaces its runtime
behaviour.

ConfigurationClassPostProcessor does implement this new interface and
computes a mapping of the ImportAware configuration classes. The mapping
is generated for latter reuse by ImportAwareAotBeanPostProcessor.

Closes gh-2811

spring-beans/src/main/java/org/springframework/beans/factory/generator/AotContributingBeanFactoryPostProcessor.java

@@ -0,0 +1,49 @@
+/*
+ * 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.factory.generator;
+
+import org.springframework.beans.BeansException;
+import org.springframework.beans.factory.config.BeanFactoryPostProcessor;
+import org.springframework.beans.factory.config.ConfigurableListableBeanFactory;
+import org.springframework.lang.Nullable;
+
+/**
+ * Specialization of {@link BeanFactoryPostProcessor} that contributes bean
+ * factory optimizations ahead of time, using generated code that replaces
+ * runtime behavior.
+ *
+ * @author Stephane Nicoll
+ * @since 6.0
+ */
+@FunctionalInterface
+public interface AotContributingBeanFactoryPostProcessor extends BeanFactoryPostProcessor {
+
+	/**
+	 * Contribute a {@link BeanFactoryContribution} for the given bean factory,
+	 * if applicable.
+	 * @param beanFactory the bean factory to optimize
+	 * @return the contribution to use or {@code null}
+	 */
+	@Nullable
+	BeanFactoryContribution contribute(ConfigurableListableBeanFactory beanFactory);
+
+	@Override
+	default void postProcessBeanFactory(ConfigurableListableBeanFactory beanFactory) throws BeansException {
+
+	}
+
+}