Make MlDeprecationIT delete system indices before generic cleanup

The generic post test cleanup code causes deprecation warnings
when deleting system indices. This is particularly problematic
for deprecation plugin integration tests.

This change makes the ML test in the deprecation plugin integration
tests clean up the ML system indices before the generic post test
cleanup runs.

Fixes elastic#79058

x-pack/plugin/deprecation/qa/rest/src/javaRestTest/java/org/elasticsearch/xpack/deprecation/MlDeprecationIT.java

@@ -13,6 +13,8 @@
 import org.elasticsearch.client.RestClient;
 import org.elasticsearch.client.RestHighLevelClient;
 import org.elasticsearch.client.WarningsHandler;
+import org.elasticsearch.client.feature.ResetFeaturesRequest;
+import org.elasticsearch.client.feature.ResetFeaturesResponse;
 import org.elasticsearch.client.migration.DeprecationInfoRequest;
 import org.elasticsearch.client.migration.DeprecationInfoResponse;
 import org.elasticsearch.client.ml.PutJobRequest;
@@ -25,9 +27,11 @@
 import org.elasticsearch.test.rest.ESRestTestCase;
 import org.elasticsearch.xcontent.NamedXContentRegistry;
 import org.elasticsearch.xcontent.XContentType;
+import org.junit.After;
 
 import java.util.ArrayList;
 import java.util.Collections;
+import java.util.List;
 import java.util.Map;
 
 import static org.hamcrest.Matchers.containsString;
@@ -57,6 +61,29 @@ protected boolean enableWarningsCheck() {
         return false;
     }
 
+    /**
+     * Currently the generic test cleanup code that runs in between tests is causing deprecation warnings
+     * when it deletes system indices like .ml-config. This causes particular problems within this test
+     * suite that's specifically testing for deprecations. Therefore, before the generic cleanup code runs,
+     * ensure that all ML system indices are already deleted.
+     *
+     * TODO: delete this method once the generic cleanup code deletes system indices without generating
+     *       deprecation warnings.
+     */
+    @After
+    public void resetFeatures() throws Exception {
+        HLRC adminHlrc = new HLRC(adminClient());
+        List<ResetFeaturesResponse.ResetFeatureStateStatus> statuses = adminHlrc.features()
+            .resetFeatures(new ResetFeaturesRequest(), RequestOptions.DEFAULT)
+            .getFeatureResetStatuses();
+        for (ResetFeaturesResponse.ResetFeatureStateStatus status : statuses) {
+            if ("machine_learning".equals(status.getFeatureName()) && status.getException() != null) {
+                throw status.getException();
+            }
+        }
+        // It's deliberate not to close the admin client
+    }
+
     public void testMlDeprecationChecks() throws Exception {
         HLRC hlrc = new HLRC(client());
         String jobId = "deprecation_check_job";
@@ -99,5 +126,4 @@ public void testMlDeprecationChecks() throws Exception {
         assertThat(response.getMlSettingsIssues().get(0).getMeta(), equalTo(Map.of("job_id", jobId, "snapshot_id", "1")));
         hlrc.close();
     }
-
 }