[TEST] Migrated ccs-unavailable-clusters QA tests (elastic#114764)

Ccs-unavailable-clusters QA tests migrated to the new REST testing
framework, using 'elasticsearch.internal-java-rest-test' Gradle plugin

Author: jozala

qa/ccs-unavailable-clusters/build.gradle

@@ -6,9 +6,12 @@
  * your election, the "Elastic License 2.0", the "GNU Affero General Public
  * License v3.0 only", or the "Server Side Public License, v 1".
  */
-apply plugin: 'elasticsearch.legacy-java-rest-test'
 
-testClusters.matching { it.name == "javaRestTest" }.configureEach {
-  setting 'xpack.security.enabled', 'true'
-  user username: 'admin', password: 'admin-password', role: 'superuser'
+import org.elasticsearch.gradle.testclusters.StandaloneRestIntegTestTask
+
+apply plugin: 'elasticsearch.internal-java-rest-test'
+
+
+tasks.withType(StandaloneRestIntegTestTask) {
+  usesDefaultDistribution()
 }

qa/ccs-unavailable-clusters/src/javaRestTest/java/org/elasticsearch/search/CrossClusterSearchUnavailableClusterIT.java

@@ -38,13 +38,15 @@
 import org.elasticsearch.common.util.concurrent.EsExecutors;
 import org.elasticsearch.common.util.concurrent.ThreadContext;
 import org.elasticsearch.search.aggregations.InternalAggregations;
+import org.elasticsearch.test.cluster.ElasticsearchCluster;
 import org.elasticsearch.test.rest.ESRestTestCase;
 import org.elasticsearch.test.rest.ObjectPath;
 import org.elasticsearch.test.transport.MockTransportService;
 import org.elasticsearch.threadpool.TestThreadPool;
 import org.elasticsearch.threadpool.ThreadPool;
 import org.elasticsearch.xcontent.XContentBuilder;
 import org.elasticsearch.xcontent.json.JsonXContent;
+import org.junit.ClassRule;
 
 import java.io.IOException;
 import java.util.Collections;
@@ -61,6 +63,14 @@ public class CrossClusterSearchUnavailableClusterIT extends ESRestTestCase {
 
     private final ThreadPool threadPool = new TestThreadPool(getClass().getName());
 
+    @ClassRule
+    public static ElasticsearchCluster cluster = ElasticsearchCluster.local().build();
+
+    @Override
+    protected String getTestRestCluster() {
+        return cluster.getHttpAddresses();
+    }
+
     @Override
     public void tearDown() throws Exception {
         super.tearDown();