### Description

Currently, when we execute retention policy, we also refresh the destination index by setting:
```
setRefresh(true)
```
on the DBQ request.
This can cause permission errors which are surprising to the user as the permissions are not required when the transform starts:
```
task encountered irrecoverable failure: org.elasticsearch.ElasticsearchSecurityException: action [indices:admin/refresh] is unauthorized for user [found-internal-kibana4-server] with roles [kibana_system,found-internal-kibana4-server] on indices [logs-cloud_security_posture.findings_latest-default], this action is granted by the index privileges [maintenance,manage,all]
```

We still want the user to have the permissions to delete the documents. But we should execute `refresh` as the system user.
x-pack/plugin/transform/src/main/java/org/elasticsearch/xpack/transform/transforms/TransformIndexer.java
import org.elasticsearch.action.index.IndexRequest;
import org.elasticsearch.action.search.SearchRequest;
import org.elasticsearch.action.search.SearchResponse;
import org.elasticsearch.action.support.IndicesOptions;
import org.elasticsearch.common.breaker.CircuitBreakingException;
import org.elasticsearch.common.logging.LoggerMessageFormat;
import org.elasticsearch.common.util.CollectionUtils;
import org.elasticsearch.core.Tuple;
import org.elasticsearch.index.query.BoolQueryBuilder;
import org.elasticsearch.index.query.QueryBuilder;
import org.elasticsearch.index.query.QueryBuilders;
import org.elasticsearch.index.reindex.BulkByScrollResponse;
import org.elasticsearch.index.reindex.DeleteByQueryRequest;
import org.elasticsearch.script.ScriptException;
import org.elasticsearch.search.builder.SearchSourceBuilder;
import org.elasticsearch.threadpool.ThreadPool;
import org.elasticsearch.xpack.core.indexing.AsyncTwoPhaseIndexer;
import org.elasticsearch.xpack.core.indexing.IndexerState;
import org.elasticsearch.xpack.core.indexing.IterationResult;
import org.elasticsearch.xpack.core.transform.TransformMessages;
import org.elasticsearch.xpack.core.transform.transforms.SettingsConfig;
import org.elasticsearch.xpack.core.transform.transforms.TransformCheckpoint;
import org.elasticsearch.xpack.core.transform.transforms.TransformConfig;
import org.elasticsearch.xpack.core.transform.transforms.TransformIndexerPosition;
import org.elasticsearch.xpack.core.transform.transforms.TransformIndexerStats;
import org.elasticsearch.xpack.core.transform.transforms.TransformProgress;
import org.elasticsearch.xpack.core.transform.transforms.TransformState;
import org.elasticsearch.xpack.core.transform.transforms.TransformTaskState;
import org.elasticsearch.xpack.core.transform.utils.ExceptionsHelper;
import org.elasticsearch.xpack.transform.TransformServices;