Add support for Async invocation in a native image

This commit adds necessary hints so that Async-annotated method can be
discovered in a native image.

Closes gh-28710

spring-context/src/main/java/org/springframework/scheduling/annotation/Async.java

@@ -22,6 +22,8 @@ import java.lang.annotation.Retention;
 import java.lang.annotation.RetentionPolicy;
 import java.lang.annotation.Target;
 
+import org.springframework.aot.hint.annotation.Reflective;
+
 /**
  * Annotation that marks a method as a candidate for <i>asynchronous</i> execution.
  *
@@ -54,6 +56,7 @@ import java.lang.annotation.Target;
 @Target({ElementType.TYPE, ElementType.METHOD})
 @Retention(RetentionPolicy.RUNTIME)
 @Documented
+@Reflective
 public @interface Async {
 
 	/**

spring-context/src/main/java/org/springframework/scheduling/annotation/SchedulingRuntimeHints.java

@@ -0,0 +1,37 @@
+/*
+ * 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.scheduling.annotation;
+
+import org.springframework.aot.hint.RuntimeHints;
+import org.springframework.aot.hint.RuntimeHintsRegistrar;
+import org.springframework.aot.hint.support.RuntimeHintsUtils;
+import org.springframework.lang.Nullable;
+
+/**
+ * {@link RuntimeHintsRegistrar} for scheduling annotations.
+ *
+ * @author Stephane Nicoll
+ * @since 6.0
+ */
+class SchedulingRuntimeHints implements RuntimeHintsRegistrar {
+
+	@Override
+	public void registerHints(RuntimeHints hints, @Nullable ClassLoader classLoader) {
+		RuntimeHintsUtils.registerAnnotation(hints, Async.class);
+	}
+
+}