Add RuntimeHintsAgent Java agent

With the introduction of `RuntimeHints`, we can now contribute
reflection, resources and proxies hints that describe the expected
runtime behavior of the application. While this can be verified at
runtime with smoke tests, managing such tests and compiling to native
there is not very efficient.

This commit introduces the new `RuntimeHintsAgent`, a Java agent that
instruments JDK methods related to `RuntimeHints`.
It is different from the GraalVM agent, which aims at collecting all the
required hints for the runtime behavior of an application and dump those
in the expected format.
Here, the `RuntimeHintsAgent` can collect the related invocations only
for a delimited scope (typically, a lambda within a test) and later
check those against a `RuntimeHints` instance. In the case of testing
`RuntimeHintsRegistrar` implementations, the process is reversed:
instead of manually checking for registered hints in a `RuntimeHints`
instance, tests should exercise the use cases and then check that the
recorded behavior is in line with the prepared hints.

This first commit adds the agent infrastructure that collects the
invocations for all relevant JDK methods.

See gh-27981

Author: bclozel

spring-core-test/spring-core-test.gradle

@@ -2,9 +2,19 @@ description = "Spring Core Test"
 
 dependencies {
 	api(project(":spring-core"))
+	api("org.junit.jupiter:junit-jupiter-api")
 	api("org.assertj:assertj-core")
 	api("com.thoughtworks.qdox:qdox")
 	compileOnly("org.junit.jupiter:junit-jupiter")
 	compileOnly("org.junit.platform:junit-platform-engine")
 	compileOnly("org.junit.platform:junit-platform-launcher")
 }
+
+jar {
+	manifest {
+		attributes(
+				'Premain-Class': 'org.springframework.aot.agent.RuntimeHintsAgent',
+				'Can-Redefine-Classes': 'true'
+		)
+	}
+}

spring-core-test/src/main/java/org/springframework/aot/agent/HintType.java

@@ -0,0 +1,76 @@
+/*
+ * 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.aot.agent;
+
+
+import org.springframework.aot.hint.ClassProxyHint;
+import org.springframework.aot.hint.JavaSerializationHint;
+import org.springframework.aot.hint.JdkProxyHint;
+import org.springframework.aot.hint.ReflectionHints;
+import org.springframework.aot.hint.ResourceBundleHint;
+import org.springframework.aot.hint.ResourcePatternHint;
+
+/**
+ * Main types of {@link org.springframework.aot.hint.RuntimeHints}.
+ * <p>This allows to sort {@link RecordedInvocation recorded invocations}
+ * into hint categories.
+ *
+ * @author Brian Clozel
+ * @since 6.0
+ */
+public enum HintType {
+
+	/**
+	 * Reflection hint, as described by {@link org.springframework.aot.hint.ReflectionHints}.
+	 */
+	REFLECTION(ReflectionHints.class),
+
+	/**
+	 * Resource pattern hint, as described by {@link org.springframework.aot.hint.ResourceHints#resourcePatterns()}.
+	 */
+	RESOURCE_PATTERN(ResourcePatternHint.class),
+
+	/**
+	 * Resource bundle hint, as described by {@link org.springframework.aot.hint.ResourceHints#resourceBundles()}.
+	 */
+	RESOURCE_BUNDLE(ResourceBundleHint.class),
+
+	/**
+	 * Java serialization hint, as described by {@link org.springframework.aot.hint.JavaSerializationHint}.
+	 */
+	JAVA_SERIALIZATION(JavaSerializationHint.class),
+
+	/**
+	 * JDK proxies hint, as described by {@link org.springframework.aot.hint.ProxyHints#jdkProxies()}.
+	 */
+	JDK_PROXIES(JdkProxyHint.class),
+
+	/**
+	 * Class proxies hint, as described by {@link org.springframework.aot.hint.ProxyHints#classProxies()}.
+	 */
+	CLASS_PROXIES(ClassProxyHint.class);
+
+	private final Class<?> hintClass;
+
+	HintType(Class<?> hintClass) {
+		this.hintClass = hintClass;
+	}
+
+	public String hintClassName() {
+		return this.hintClass.getSimpleName();
+	}
+}