### CI Link

https://gradle-enterprise.elastic.co/s/oyi6h23yl6k3o/tests/:x-pack:qa:full-cluster-restart:v8.11.0%23bwcTest/org.elasticsearch.xpack.restart.CoreFullClusterRestartIT/testClusterState%20%7Bcluster=OLD%7D

### Repro line

./gradlew ':qa:full-cluster-restart:v8.11.0#bwcTest' -Dtests.class="org.elasticsearch.upgrades.FullClusterRestartIT"

### Does it reproduce?

Yes

### Applicable branches

main

### Failure history

_No response_

### Failure excerpt

This test assumes that the index created version in cluster state matches the old node version.

That is no longer true due to the introduction of `IndexVersion`

https://github.com/elastic/elasticsearch/blob/52a6820813577abcb23191d862a01e32e652ed42/qa/full-cluster-restart/src/javaRestTest/java/org/elasticsearch/upgrades/FullClusterRestartIT.java#L435-L440
qa/full-cluster-restart/src/javaRestTest/java/org/elasticsearch/upgrades/FullClusterRestartIT.java
Map<?, ?> bestHit = (Map<?, ?>) ((List<?>) (XContentMapValues.extractValue("hits.hits", response))).get(0);
        
        
        String stringValue = (String) XContentMapValues.extractValue("_source.string", bestHit);
        assertNotNull(stringValue);
        String id = (String) bestHit.get("_id");
        Request explainRequest = new Request("GET", "/" + index + "/_explain/" + id);
        explainRequest.setJsonEntity("{ \"query\": { \"match_all\" : {} }}");
        String explanation = toStr(client().performRequest(explainRequest));
        assertFalse("Could not find payload boost in explanation\n" + explanation, explanation.contains("payloadBoost"));
        
        Request searchRequest = new Request("GET", "/" + index + "/_search");
        searchRequest.setEntity(explainRequest.getEntity());
        searchRequest.addParameter("explain", "true");
        Map<?, ?> matchAllResponse = entityAsMap(client().performRequest(searchRequest));
        assertNoFailures(matchAllResponse);
        assertTotalHits(count, matchAllResponse);
    }
    void assertBasicAggregationWorks() throws IOException {
        
        Request longHistogramRequest = new Request("GET", "/" + index + "/_search");
        longHistogramRequest.setJsonEntity("""
            {
              "aggs": {
                "histo": {
                  "histogram": {
                    "field": "int",
                    "interval": 10
                  }
                }