### 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
if (shouldStopAtCheckpoint && initialRun() && indexerState.equals(IndexerState.STARTED)) {
            indexerState = IndexerState.STOPPED;
            auditor.info(transformConfig.getId(), "Transform is no longer in the middle of a checkpoint, initiating stop.");
            logger.info("[{}] transform is no longer in the middle of a checkpoint, initiating stop.", transformConfig.getId());
        }
        
        
        
        if (hasSourceChanged == false && indexerState.equals(IndexerState.STOPPED) == false) {
            if (saveStateListenersAtTheMomentOfCalling != null) {
                ActionListener.onResponse(saveStateListenersAtTheMomentOfCalling, null);
            }
            next.run();
            return;
        }
        TransformTaskState taskState = context.getTaskState();
        if (indexerState.equals(IndexerState.STARTED) && context.getCheckpoint() == 1 && this.isContinuous() == false) {
            
            indexerState = IndexerState.STOPPED;
            auditor.info(transformConfig.getId(), "Transform finished indexing all data, initiating stop");
            logger.info("[{}] transform finished indexing all data, initiating stop.", transformConfig.getId());
        }
        
        
        
        if (indexerState.equals(IndexerState.STOPPED)) {