2nd attempt at https://github.com/elastic/elasticsearch/issues/84591

references https://github.com/elastic/elasticsearch/issues/48856#issuecomment-831144741

tldr; the permission structure for the endpoint isn't useful for most users. If users can create runtime fields they should have access to this api, they shouldn't need a specific permission set. 
x-pack/qa/runtime-fields/with-security/src/javaRestTest/java/org/elasticsearch/xpack/security/PermissionsIT.java
""");
        assertOK(adminClient().performRequest(indexDoc2));
        Request indexDoc3 = new Request("PUT", "/dls/_doc/3");
        indexDoc3.addParameter("refresh", "true");
        indexDoc3.setJsonEntity("""
            {
                "date" : "2018-11-15T14:12:12"
            }
            """);
        assertOK(adminClient().performRequest(indexDoc3));
        SearchRequest searchRequest = new SearchRequest("dls");
        {
            SearchResponse searchResponse = adminHighLevelClient.search(searchRequest, RequestOptions.DEFAULT);
            assertEquals(3, searchResponse.getHits().getTotalHits().value);
        }
        {
            SearchResponse searchResponse = highLevelClient.search(searchRequest, RequestOptions.DEFAULT);
            assertEquals(1, searchResponse.getHits().getTotalHits().value);
        }
    }
    public void testFLSProtectsData() throws IOException {
        Request createIndex = new Request("PUT", "/fls");
        createIndex.setJsonEntity("""
            {
                "mappings" : {
                    "runtime" : {
                        "hidden_values_count" : {
                          "type" : "long",\s
                          "script" : "emit(doc['hidden'].size())"
                        }