### 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
logger.trace("[{}] reset the progress from [{}] to [{}].", getJobId(), progress, newProgress);
                            progress = newProgress != null ? newProgress : new TransformProgress();
                            finalListener.onResponse(null);
                        }, failure -> {
                            progress = new TransformProgress();
                            logger.warn(() -> "[" + getJobId() + "] unable to load progress information for task.", failure);
                            finalListener.onResponse(null);
                        }));
                    }, failure -> {
                        progress = new TransformProgress();
                        logger.warn(() -> "[" + getJobId() + "] unable to load progress information for task.", failure);
                        finalListener.onResponse(null);
                    }));
                }, listener::onFailure));
            } else {
                finalListener.onResponse(null);
            }
        }, listener::onFailure);
        ActionListener<Map<String, String>> fieldMappingsListener = ActionListener.wrap(mappings -> {
            this.fieldMappings = mappings;
            configurationReadyListener.onResponse(null);
        }, listener::onFailure);
        ActionListener<Void> reLoadFieldMappingsListener = ActionListener.wrap(
            updateConfigResponse -> { doGetFieldMappings(fieldMappingsListener); },
            listener::onFailure
        );
        
        ActionListener<Void> changedSourceListener = ActionListener.wrap(r -> {
            if (isContinuous()) {
                transformsConfigManager.getTransformConfiguration(getJobId(), ActionListener.wrap(config -> {