Fix classpath index so entries match those expected by the launcher

This reverts commit ad164269e9 and adds
some additional tests.

Fixes gh-24192

spring-boot-project/spring-boot-tools/spring-boot-gradle-plugin/src/test/java/com/example/bootjar/classpath/BootJarClasspathApplication.java

@@ -0,0 +1,41 @@
+/*
+ * Copyright 2012-2019 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 com.example.bootjar.classpath;
+
+import java.net.URL;
+import java.net.URLClassLoader;
+
+/**
+ * Application used for testing classpath handling with BootJar.
+ *
+ * @author Andy Wilkinson
+ */
+public class BootJarClasspathApplication {
+
+	protected BootJarClasspathApplication() {
+
+	}
+
+	public static void main(String[] args) {
+		int i = 1;
+		ClassLoader classLoader = Thread.currentThread().getContextClassLoader();
+		for (URL url : ((URLClassLoader) classLoader).getURLs()) {
+			System.out.println(i++ + ". " + url.getFile());
+		}
+	}
+
+}

spring-boot-project/spring-boot-tools/spring-boot-gradle-plugin/src/test/java/com/example/bootrun/classpath/BootRunClasspathApplication.java

@@ -14,7 +14,7 @@
  * limitations under the License.
  */
 
-package com.example.classpath;
+package com.example.bootrun.classpath;
 
 import java.io.File;
 import java.lang.management.ManagementFactory;

spring-boot-project/spring-boot-tools/spring-boot-gradle-plugin/src/test/java/com/example/bootrun/jvmargs/BootRunJvmArgsApplication.java

@@ -14,7 +14,7 @@
  * limitations under the License.
  */
 
-package com.example.jvmargs;
+package com.example.bootrun.jvmargs;
 
 import java.lang.management.ManagementFactory;