Introduce AotTestExecutionListener API in the TestContext framework

This commit introduces an AotTestExecutionListener API that extends
TestExecutionListener and allows a TestExecutionListener to opt in for
AOT processing support, analogous to what the AotContextLoader API does
for a SmartContextLoader.

Closes gh-29070

spring-test/src/main/java/org/springframework/test/context/aot/AotTestExecutionListener.java

@@ -0,0 +1,42 @@
+/*
+ * 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.test.context.aot;
+
+import org.springframework.aot.hint.RuntimeHints;
+import org.springframework.test.context.TestExecutionListener;
+
+/**
+ * {@code AotTestExecutionListener} is an extension of the {@link TestExecutionListener}
+ * SPI that allows a listener to optionally provide ahead-of-time (AOT) support.
+ *
+ * @author Sam Brannen
+ * @since 6.0
+ */
+public interface AotTestExecutionListener extends TestExecutionListener {
+
+	/**
+	 * Process the supplied test class ahead-of-time using the given
+	 * {@link RuntimeHints} instance.
+	 * <p>If possible, implementations should use the specified {@link ClassLoader}
+	 * to determine if hints have to be contributed.
+	 * @param testClass the test class to process
+	 * @param runtimeHints the {@code RuntimeHints} to use
+	 * @param classLoader the classloader to use
+	 */
+	void processAheadOfTime(Class<?> testClass, RuntimeHints runtimeHints, ClassLoader classLoader);
+
+}

spring-test/src/main/java/org/springframework/test/context/aot/TestContextAotGenerator.java

@@ -210,9 +210,12 @@ MergedContextConfiguration buildMergedContextConfiguration(Class<?> testClass) {
 		// @BootstrapWith
 		registerDeclaredConstructors(testContextBootstrapper.getClass());
 		// @TestExecutionListeners
-		testContextBootstrapper.getTestExecutionListeners().stream()
-				.map(Object::getClass)
-				.forEach(this::registerDeclaredConstructors);
+		testContextBootstrapper.getTestExecutionListeners().forEach(listener -> {
+			registerDeclaredConstructors(listener.getClass());
+			if (listener instanceof AotTestExecutionListener aotListener) {
+				aotListener.processAheadOfTime(testClass, this.runtimeHints, getClass().getClassLoader());
+			}
+		});
 		return testContextBootstrapper.buildMergedContextConfiguration();
 	}