Moved workflow samples out of .github/workflows

The `.github/workflows` directory has additional permissions attached, preventing these
files from being by the Upgrade Gradle Wrapper plugin.

.github/workflow-samples/gradle-plugin/plugin/src/functionalTest/java/org/example/gradle/plugin/GradlePluginPluginFunctionalTest.java

@@ -0,0 +1,57 @@
+/*
+ * This Java source file was generated by the Gradle 'init' task.
+ */
+package org.example.gradle.plugin;
+
+import java.io.File;
+import java.io.IOException;
+import java.io.Writer;
+import java.io.FileWriter;
+import java.nio.file.Files;
+import org.gradle.testkit.runner.GradleRunner;
+import org.gradle.testkit.runner.BuildResult;
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.api.io.TempDir;
+import static org.junit.jupiter.api.Assertions.*;
+
+/**
+ * A simple functional test for the 'org.example.gradle.plugin.greeting' plugin.
+ */
+class GradlePluginPluginFunctionalTest {
+    @TempDir
+    File projectDir;
+
+    private File getBuildFile() {
+        return new File(projectDir, "build.gradle");
+    }
+
+    private File getSettingsFile() {
+        return new File(projectDir, "settings.gradle");
+    }
+
+    @Test void canRunTaskWithGradle691() throws IOException {
+        writeString(getSettingsFile(), "");
+        writeString(getBuildFile(),
+            "plugins {" +
+            "  id('org.example.gradle.plugin.greeting')" +
+            "}");
+
+        // Run the build
+        GradleRunner runner = GradleRunner.create();
+        runner.forwardOutput();
+        runner.withGradleVersion("6.9.1");
+        runner.withPluginClasspath();
+        runner.withArguments("greeting");
+        runner.withProjectDir(projectDir);
+        BuildResult result = runner.build();
+
+        // Verify the result
+        assertTrue(result.getOutput().contains("Hello from plugin 'org.example.gradle.plugin.greeting'"));
+    }
+
+    private void writeString(File file, String string) throws IOException {
+        try (Writer writer = new FileWriter(file)) {
+            writer.write(string);
+        }
+    }
+}

.github/workflow-samples/gradle-plugin/plugin/src/main/java/org/example/gradle/plugin/GradlePluginPlugin.java

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+/*
+ * This Java source file was generated by the Gradle 'init' task.
+ */
+package org.example.gradle.plugin;
+
+import org.gradle.api.Project;
+import org.gradle.api.Plugin;
+
+/**
+ * A simple 'hello world' plugin.
+ */
+public class GradlePluginPlugin implements Plugin<Project> {
+    public void apply(Project project) {
+        // Register a task
+        project.getTasks().register("greeting", task -> {
+            task.doLast(s -> System.out.println("Hello from plugin 'org.example.gradle.plugin.greeting'"));
+        });
+    }
+}

.github/workflow-samples/gradle-plugin/plugin/src/test/java/org/example/gradle/plugin/GradlePluginPluginTest.java

@@ -0,0 +1,23 @@
+/*
+ * This Java source file was generated by the Gradle 'init' task.
+ */
+package org.example.gradle.plugin;
+
+import org.gradle.testfixtures.ProjectBuilder;
+import org.gradle.api.Project;
+import org.junit.jupiter.api.Test;
+import static org.junit.jupiter.api.Assertions.*;
+
+/**
+ * A simple unit test for the 'org.example.gradle.plugin.greeting' plugin.
+ */
+class GradlePluginPluginTest {
+    @Test void pluginRegistersATask() {
+        // Create a test project and apply the plugin
+        Project project = ProjectBuilder.builder().build();
+        project.getPlugins().apply("org.example.gradle.plugin.greeting");
+
+        // Verify the result
+        assertNotNull(project.getTasks().findByName("greeting"));
+    }
+}