Part of https://github.com/elastic/kibana/issues/153483

We have identified a problem with the index template/ILM policy structure so we need to stop the ILM policy from rolling over while we get a long term fix.

In investigating this I also noticed that the index templates do not set `hidden` to be true which they should.


x-pack/plugin/fleet/src/javaRestTest/java/org/elasticsearch/xpack/fleet/FleetSystemIndicesIT.java
@SuppressWarnings("unchecked")
    public void verifyFilesILMPolicyExists() throws Exception {
        assertBusy(() -> {
            Request request = new Request("GET", "_ilm/policy/.fleet-files-ilm-policy");
            Response response = client().performRequest(request);
            assertEquals(200, response.getStatusLine().getStatusCode());
            final String responseJson = EntityUtils.toString(response.getEntity());
            Map<String, Object> responseMap = XContentHelper.convertToMap(XContentType.JSON.xContent(), responseJson, false);
            assertNotNull(responseMap.get(".fleet-files-ilm-policy"));
            Map<String, Object> policyMap = (Map<String, Object>) responseMap.get(".fleet-files-ilm-policy");
            assertNotNull(policyMap);
            assertThat(policyMap.size(), equalTo(2));
        });
    }
    @SuppressWarnings("unchecked")
    public void verifyFileDataILMPolicyExists() throws Exception {
        assertBusy(() -> {
            Request request = new Request("GET", "_ilm/policy/.fleet-file-data-ilm-policy");
            Response response = client().performRequest(request);
            assertEquals(200, response.getStatusLine().getStatusCode());
            final String responseJson = EntityUtils.toString(response.getEntity());
            Map<String, Object> responseMap = XContentHelper.convertToMap(XContentType.JSON.xContent(), responseJson, false);
            assertNotNull(responseMap.get(".fleet-file-data-ilm-policy"));
            Map<String, Object> policyMap = (Map<String, Object>) responseMap.get(".fleet-file-data-ilm-policy");
            assertNotNull(policyMap);
            assertThat(policyMap.size(), equalTo(2));
        });
    }
}