[CI] EnterpriseSearchRestIT test {p0=entsearch/90_behavioral_analytics_event_post/Post search_click analytics event - Document Only} failing about elasticsearch HOT 4 OPEN

Pinging @elastic/ent-search-eng (Team:Enterprise Search)

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Pinging @elastic/search-relevance (Team:Search - Relevance)

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Pinging @elastic/ent-search-eng (Team:SearchOrg)

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This is the only failure for this test in the last 3 months (26349 executions).
My theory is that the cluster did not finished to initialize completely before the test is started.

We could add a method to wait for the template registry to be fully installed before starting the test into org.elasticsearch.xpack.entsearch.EnterpriseSearchRestIT.

The code could be something like:

@Before
public void waitForBehavioralAnalyticsTemplateInstalled() {
    assertBusy(() -> { 
        Request getIndexTemplateRequest = new Request("GET", "_index_template/behavioral_analytics-events-default");
        Response response = client().performRequest(getIndexTemplateRequest);
        assertOK(response);
    });
}

from elasticsearch.