Wait for all cluster state updates to be processed before wiping the cluster (#104846) (#105349)

In #104846, we see an inconsistency in the state of the clusters between
the test and the clean up at the end of the test. 

The failure is as follows: - The test using ILM at some point creates a
full searchable snapshots with name `restore-my-index-xxxx` - Then ILM
moves to frozen and creates a partially searchable snapshots with alias
`restore-my-index-xxxx` - The test confirms that `restore-my-index-xxxx`
is an alias and ends - During tear down, it appears that the cluster
state retrieved contains the `restore-my-index-xxxx` as an index so it
issues a request to delete it. - The deletion fails because
`restore-my-index-xxxx` is an alias.

I do not think that the test has an issue, most of the clues shows that
the partial searchable snapshot has been correctly processed. Only this
cluster state retrieval seems a bit off. In order to reduce this
flakiness we introduce a `GET _cluster/health?wait_for_events=languid`
to ensure we get the latest cluster state.

Fixes #104846

test/framework/src/main/java/org/elasticsearch/test/rest/ESRestTestCase.java

@@ -813,6 +813,8 @@ public abstract class ESRestTestCase extends ESTestCase {
     }
 
     private void wipeCluster() throws Exception {
+        logger.info("Waiting for all cluster updates up to this moment to be processed");
+        assertOK(adminClient().performRequest(new Request("GET", "_cluster/health?wait_for_events=languid")));
 
         // Cleanup rollup before deleting indices. A rollup job might have bulks in-flight,
         // so we need to fully shut them down first otherwise a job might stall waiting