The failing test is FullClusterRestartIT testApiKeySuperuser 
This happens on my PR CI and related to my change. 

But the underlying reason seems to be upgrade failure of security system index. Cluster log shows a NPE https://gradle-enterprise.elastic.co/s/wgya6tyniu7y2/console-log#L2024 for `AliasMetadata#isHidden` invocation and comparison.
 
I suspect it has something to do with #79512 and recent enforce of 7.last for 8.x upgrade.

**Build scan:**
https://gradle-enterprise.elastic.co/s/wgya6tyniu7y2/tests/:x-pack:qa:full-cluster-restart:v7.8.1%23upgradedClusterTest/org.elasticsearch.xpack.restart.FullClusterRestartIT/testApiKeySuperuser

**Reproduction line:**
`./gradlew ':x-pack:qa:full-cluster-restart:v7.8.1#upgradedClusterTest' -Dtests.class="org.elasticsearch.xpack.restart.FullClusterRestartIT" -Dtests.method="testApiKeySuperuser" -Dtests.seed=704325F309264EE2 -Dtests.bwc=true -Dtests.locale=fi -Dtests.timezone=America/Boise -Druntime.java=17`

**Applicable branches:**
master

**Reproduces locally?:**
Yes

**Failure history:**
https://gradle-enterprise.elastic.co/scans/tests?tests.container=org.elasticsearch.xpack.restart.FullClusterRestartIT&tests.test=testApiKeySuperuser

**Failure excerpt:**
```
org.elasticsearch.client.WarningFailureException: method [GET], host [http://127.0.0.1:42205], URI [.security/_search], status line [HTTP/1.1 200 OK]
{"took":2,"timed_out":false,"_shards":{"total":1,"successful":1,"skipped":0,"failed":0},"hits":{"total":{"value":4,"relation":"eq"},"max_score":1.0,"hits":[{"_index":".security-7","_id":"user-api_key_super_creator","_score":1.0,"_source":{"username":"api_key_super_creator","password":"$2a$10$OsBKVjcqgvziPdsewcOcmufqeJNjplujZ8NYFW6sjL2VXdVfTgpMe","roles":["superuser","monitoring_user"],"full_name":null,"email":null,"metadata":null,"enabled":true,"type":"user"}},{"_index":".security-7","_id":"_mHGdH4B2CIXTYmcz0_9","_score":1.0,"_source":{"doc_type":"api_key","creation_time":1642636693479,"expiration_time":null,"api_key_invalidated":false,"api_key_hash":"{PBKDF2}10000$v4R2re60QvaorlE+Cwl0MRq2uIE0rABYIrmBSMAxs4U=$yDhHqMHGzXtVgb4CPnGAdtKRMxP+nzpP0L4zdT45pPw=","role_descriptors":{},"limited_by_role_descriptors":{"superuser":{"cluster":["all"],"indices":[{"names":["*"],"privileges":["all"],"allow_restricted_indices":true}],"applications":[{"application":"*","privileges":["*"],"resources":["*"]}],"run_as":["*"],"metadata":{"_reserved":true},"type":"role"},"monitoring_user":{"cluster":["cluster:monitor/main","cluster:monitor/xpack/info","cluster:monitor/remote/info"],"indices":[{"names":[".monitoring-*"],"privileges":["read","read_cross_cluster"],"allow_restricted_indices":false}],"applications":[{"application":"kibana-*","privileges":["reserved_monitoring"],"resources":["*"]}],"run_as":[],"metadata":{"_reserved":true},"type":"role"}},"name":"super_legacy_key","version":7080199,"creator":{"principal":"api_key_super_creator","metadata":{},"realm":"default_native","realm_type":"native"}}},{"_index":".security-7","_id":"9aTGdH4B8Erq23pH0QLn","_score":1.0,"_source":{
  "doc_type": "foo"
}},{"_index":".security-7","_id":"AGHGdH4B2CIXTYmc1FBS","_score":1.0,"_source":{"doc_type":"api_key","creation_time":1642636694588,"expiration_time":null,"api_key_invalidated":false,"api_key_hash":"{PBKDF2}10000$Uj+vKfhGVDJ+0dM+YBDyJIsC2hSFGXCqojoMQ6Ens9E=$/8X0Dup+8cwgm1L5d5zNHtUPoDG1fV1WCPhcPu1p4yg=","role_descriptors":{"r":{"cluster":["all"],"indices":[{"names":["*"],"privileges":["all"],"allow_restricted_indices":false}],"applications":[],"run_as":[],"metadata":{},"type":"role"}},"limited_by_role_descriptors":{"_es_test_root":{"cluster":["ALL"],"indices":[{"names":["*"],"privileges":["ALL"],"allow_restricted_indices":true}],"applications":[{"application":"*","privileges":["*"],"resources":["*"]}],"run_as":["*"],"metadata":{},"type":"role"}},"name":"key-1","version":7080199,"creator":{"principal":"test_user","metadata":{},"realm":"default_file","realm_type":"file"}}}]}}

  at __randomizedtesting.SeedInfo.seed([704325F309264EE2:478E48673AE6CF31]:0)
  at org.elasticsearch.client.RestClient.convertResponse(RestClient.java:342)
  at org.elasticsearch.client.RestClient.performRequest(RestClient.java:312)
  at org.elasticsearch.client.RestClient.performRequest(RestClient.java:287)
  at org.elasticsearch.xpack.restart.FullClusterRestartIT.testApiKeySuperuser(FullClusterRestartIT.java:421)
  at jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(NativeMethodAccessorImpl.java:-2)
  at jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:77)
  at jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
  at java.lang.reflect.Method.invoke(Method.java:568)
  at com.carrotsearch.randomizedtesting.RandomizedRunner.invoke(RandomizedRunner.java:1758)
  at com.carrotsearch.randomizedtesting.RandomizedRunner$8.evaluate(RandomizedRunner.java:946)
  at com.carrotsearch.randomizedtesting.RandomizedRunner$9.evaluate(RandomizedRunner.java:982)
  at com.carrotsearch.randomizedtesting.RandomizedRunner$10.evaluate(RandomizedRunner.java:996)
  at com.carrotsearch.randomizedtesting.rules.StatementAdapter.evaluate(StatementAdapter.java:36)
  at org.apache.lucene.util.TestRuleSetupTeardownChained$1.evaluate(TestRuleSetupTeardownChained.java:44)
  at org.apache.lucene.util.AbstractBeforeAfterRule$1.evaluate(AbstractBeforeAfterRule.java:43)
  at org.apache.lucene.util.TestRuleThreadAndTestName$1.evaluate(TestRuleThreadAndTestName.java:45)
  at org.apache.lucene.util.TestRuleIgnoreAfterMaxFailures$1.evaluate(TestRuleIgnoreAfterMaxFailures.java:60)
  at org.apache.lucene.util.TestRuleMarkFailure$1.evaluate(TestRuleMarkFailure.java:44)
  at com.carrotsearch.randomizedtesting.rules.StatementAdapter.evaluate(StatementAdapter.java:36)
  at com.carrotsearch.randomizedtesting.ThreadLeakControl$StatementRunner.run(ThreadLeakControl.java:375)
  at com.carrotsearch.randomizedtesting.ThreadLeakControl.forkTimeoutingTask(ThreadLeakControl.java:824)
  at com.carrotsearch.randomizedtesting.ThreadLeakControl$3.evaluate(ThreadLeakControl.java:475)
  at com.carrotsearch.randomizedtesting.RandomizedRunner.runSingleTest(RandomizedRunner.java:955)
  at com.carrotsearch.randomizedtesting.RandomizedRunner$5.evaluate(RandomizedRunner.java:840)
  at com.carrotsearch.randomizedtesting.RandomizedRunner$6.evaluate(RandomizedRunner.java:891)
  at com.carrotsearch.randomizedtesting.RandomizedRunner$7.evaluate(RandomizedRunner.java:902)
  at org.apache.lucene.util.AbstractBeforeAfterRule$1.evaluate(AbstractBeforeAfterRule.java:43)
  at com.carrotsearch.randomizedtesting.rules.StatementAdapter.evaluate(StatementAdapter.java:36)
  at org.apache.lucene.util.TestRuleStoreClassName$1.evaluate(TestRuleStoreClassName.java:38)
  at com.carrotsearch.randomizedtesting.rules.NoShadowingOrOverridesOnMethodsRule$1.evaluate(NoShadowingOrOverridesOnMethodsRule.java:40)
  at com.carrotsearch.randomizedtesting.rules.NoShadowingOrOverridesOnMethodsRule$1.evaluate(NoShadowingOrOverridesOnMethodsRule.java:40)
  at com.carrotsearch.randomizedtesting.rules.StatementAdapter.evaluate(StatementAdapter.java:36)
  at com.carrotsearch.randomizedtesting.rules.StatementAdapter.evaluate(StatementAdapter.java:36)
  at org.apache.lucene.util.TestRuleAssertionsRequired$1.evaluate(TestRuleAssertionsRequired.java:53)
  at org.apache.lucene.util.AbstractBeforeAfterRule$1.evaluate(AbstractBeforeAfterRule.java:43)
  at org.apache.lucene.util.TestRuleMarkFailure$1.evaluate(TestRuleMarkFailure.java:44)
  at org.apache.lucene.util.TestRuleIgnoreAfterMaxFailures$1.evaluate(TestRuleIgnoreAfterMaxFailures.java:60)
  at org.apache.lucene.util.TestRuleIgnoreTestSuites$1.evaluate(TestRuleIgnoreTestSuites.java:47)
  at com.carrotsearch.randomizedtesting.rules.StatementAdapter.evaluate(StatementAdapter.java:36)
  at com.carrotsearch.randomizedtesting.ThreadLeakControl$StatementRunner.run(ThreadLeakControl.java:375)
  at com.carrotsearch.randomizedtesting.ThreadLeakControl.lambda$forkTimeoutingTask$0(ThreadLeakControl.java:831)
  at java.lang.Thread.run(Thread.java:833)

```
x-pack/qa/full-cluster-restart/src/test/java/org/elasticsearch/xpack/restart/FullClusterRestartIT.java
} else {
                    total = (Integer) hits.get("total");
                }
                assertThat(total, greaterThanOrEqualTo(expectedHits));
            } catch (IOException ioe) {
                if (ioe instanceof ResponseException) {
                    Response response = ((ResponseException) ioe).getResponse();
                    if (RestStatus.fromCode(response.getStatusLine().getStatusCode()) == RestStatus.SERVICE_UNAVAILABLE) {
                        fail("shards are not yet active");
                    }
                }
                throw ioe;
            }
        }, 30, TimeUnit.SECONDS);
    }
    private void startWatcher() throws Exception {
        Map<String, Object> startWatchResponse = entityAsMap(client().performRequest(new Request("POST", "_watcher/_start")));
        assertThat(startWatchResponse.get("acknowledged"), equalTo(Boolean.TRUE));
        assertBusy(() -> {
            Map<String, Object> statsWatchResponse = entityAsMap(client().performRequest(new Request("GET", "_watcher/stats")));
            List<?> states = ((List<?>) statsWatchResponse.get("stats")).stream()
                .map(o -> ((Map<?, ?>) o).get("watcher_state"))
                .collect(Collectors.toList());
            assertThat(states, everyItem(is("started")));
        });
    }
    private void stopWatcher() throws Exception {
        Map<String, Object> stopWatchResponse = entityAsMap(client().performRequest(new Request("POST", "_watcher/_stop")));
        assertThat(stopWatchResponse.get("acknowledged"), equalTo(Boolean.TRUE));
        assertBusy(() -> {