Build: Fix official plugins list (#35661)

The list of official plugins accidentally included `qa` projects like,
well, `qa` and `amazon-ec2`. This changes the mechanism that we use to
build the list and adds a test to catch this.

Closes #35623

distribution/tools/plugin-cli/src/test/java/org/elasticsearch/plugins/InstallPluginCommandTests.java

@@ -112,6 +112,7 @@ import static org.hamcrest.CoreMatchers.equalTo;
 import static org.hamcrest.Matchers.containsInAnyOrder;
 import static org.hamcrest.Matchers.containsString;
 import static org.hamcrest.Matchers.empty;
+import static org.hamcrest.Matchers.endsWith;
 import static org.hamcrest.Matchers.hasToString;
 import static org.hamcrest.Matchers.not;
 
@@ -726,7 +727,7 @@ public class InstallPluginCommandTests extends ESTestCase {
         assertInstallCleaned(env.v2());
     }
 
-    public void testOfficialPluginsHelpSorted() throws Exception {
+    public void testOfficialPluginsHelpSortedAndMissingObviouslyWrongPlugins() throws Exception {
         MockTerminal terminal = new MockTerminal();
         new InstallPluginCommand() {
             @Override
@@ -749,6 +750,9 @@ public class InstallPluginCommandTests extends ESTestCase {
                 assertTrue(prev + " < " + line, prev.compareTo(line) < 0);
                 prev = line;
                 line = reader.readLine();
+                // qa is not really a plugin and it shouldn't sneak in
+                assertThat(line, not(endsWith("qa")));
+                assertThat(line, not(endsWith("example")));
             }
         }
     }

server/build.gradle

@@ -172,9 +172,9 @@ task generateModulesList {
 }
 
 task generatePluginsList {
-  List<String> plugins = project(':plugins').subprojects
-    .findAll { it.name.contains('example') == false }
-    .collect { it.name }
+  Set<String> plugins = new TreeSet<>(project(':plugins').childProjects.keySet())
+  plugins.remove('example')
+
   File pluginsFile = new File(buildDir, 'generated-resources/plugins.txt')
   processResources.from(pluginsFile)
   inputs.property('plugins', plugins)