### 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
rolloverRequest.setJsonEntity("""
                {  "conditions": {    "max_docs": 5  }}""");
            client().performRequest(rolloverRequest);
            assertThat(
                EntityUtils.toString(client().performRequest(new Request("GET", "/_cat/indices?v")).getEntity()),
                containsString("testrollover-000002")
            );
        }
        Request countRequest = new Request("POST", "/" + index + "-*/_search");
        countRequest.addParameter("size", "0");
        Map<String, Object> count = entityAsMap(client().performRequest(countRequest));
        assertNoFailures(count);
        int expectedCount = bulkCount + (isRunningAgainstOldCluster() ? 0 : bulkCount);
        assertEquals(expectedCount, extractTotalHits(count));
    }
    void assertCountAll(int count) throws IOException {
        Map<String, Object> response = entityAsMap(client().performRequest(new Request("GET", "/" + index + "/_search")));
        assertNoFailures(response);
        int numDocs = extractTotalHits(response);
        logger.info("Found {} in old index", numDocs);
        assertEquals(count, numDocs);
    }
    void assertBasicSearchWorks(int count) throws IOException {
        logger.info("--> testing basic search");
        {
            assertCountAll(count);
        }
        logger.info("--> testing basic search with sort");
        {
            Request searchRequest = new Request("GET", "/" + index + "/_search");