Hide internal details of ActionListener impls (#94320)

The `ActionListener` interface implements its static methods using
various inner classes. These inner classes are public because interfaces
do not support package-private inner classes, although they are `final`
and only have `protected` constructors which prevent anyone else from
instantiating them. It's certainly a mistake for code in other packages
to access these things.

This commit moves the implementation details into a separate class to
hide them from the rest of the world. It also tightens up the calls to
`onFailure()` in a few places to better handle the possibility of this
method throwing an exception. Finally, it moves
`DelegatingActionListener` to a top level public class since this
utility is used in quite a number of places.

modules/rank-eval/src/main/java/org/elasticsearch/index/rankeval/TransportRankEvalAction.java

@@ -9,6 +9,7 @@
 package org.elasticsearch.index.rankeval;
 
 import org.elasticsearch.action.ActionListener;
+import org.elasticsearch.action.DelegatingActionListener;
 import org.elasticsearch.action.search.MultiSearchRequest;
 import org.elasticsearch.action.search.MultiSearchResponse;
 import org.elasticsearch.action.search.MultiSearchResponse.Item;
@@ -143,7 +144,7 @@ protected void doExecute(Task task, RankEvalRequest request, ActionListener<Rank
         );
     }
 
-    static class RankEvalActionListener extends ActionListener.Delegating<MultiSearchResponse, RankEvalResponse> {
+    static class RankEvalActionListener extends DelegatingActionListener<MultiSearchResponse, RankEvalResponse> {
 
         private final RatedRequest[] specifications;
 

modules/reindex/src/test/java/org/elasticsearch/reindex/ClientScrollableHitSourceTests.java

@@ -19,6 +19,7 @@
 import org.elasticsearch.action.search.SearchResponse;
 import org.elasticsearch.action.search.SearchScrollAction;
 import org.elasticsearch.action.search.SearchScrollRequest;
+import org.elasticsearch.action.support.PlainActionFuture;
 import org.elasticsearch.client.internal.ParentTaskAssigningClient;
 import org.elasticsearch.client.internal.support.AbstractClient;
 import org.elasticsearch.common.bytes.BytesArray;
@@ -48,7 +49,6 @@
 
 import static org.apache.lucene.tests.util.TestUtil.randomSimpleString;
 import static org.elasticsearch.core.TimeValue.timeValueSeconds;
-import static org.hamcrest.Matchers.instanceOf;
 
 public class ClientScrollableHitSourceTests extends ESTestCase {
 
@@ -74,19 +74,12 @@ public void testRetrySuccess() throws InterruptedException {
         dotestBasicsWithRetry(retries, 0, retries, e -> fail());
     }
 
-    private static class ExpectedException extends RuntimeException {
-        ExpectedException(Throwable cause) {
-            super(cause);
-        }
-    }
-
     public void testRetryFail() {
         int retries = randomInt(10);
-        ExpectedException ex = expectThrows(
-            ExpectedException.class,
-            () -> { dotestBasicsWithRetry(retries, retries + 1, retries + 1, e -> { throw new ExpectedException(e); }); }
+        expectThrows(
+            EsRejectedExecutionException.class,
+            () -> PlainActionFuture.get(f -> dotestBasicsWithRetry(retries, retries + 1, retries + 1, f::onFailure), 0, TimeUnit.SECONDS)
         );
-        assertThat(ex.getCause(), instanceOf(EsRejectedExecutionException.class));
     }
 
     private void dotestBasicsWithRetry(int retries, int minFailures, int maxFailures, Consumer<Exception> failureHandler)
@@ -110,6 +103,9 @@ private void dotestBasicsWithRetry(int retries, int minFailures, int maxFailures
         hitSource.start();
         for (int retry = 0; retry < randomIntBetween(minFailures, maxFailures); ++retry) {
             client.fail(SearchAction.INSTANCE, new EsRejectedExecutionException());
+            if (retry >= retries) {
+                return;
+            }
             client.awaitOperation();
             ++expectedSearchRetries;
         }