### 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
} else {
                    finalizeCheckpoint(failureHandlingListener);
                }
            }, failureHandlingListener::onFailure));
        } catch (Exception e) {
            failureHandlingListener.onFailure(e);
        }
    }
    private void executeRetentionPolicy(ActionListener<Void> listener) {
        DeleteByQueryRequest deleteByQuery = RetentionPolicyToDeleteByQueryRequestConverter.buildDeleteByQueryRequest(
            transformConfig.getRetentionPolicyConfig(),
            transformConfig.getSettings(),
            transformConfig.getDestination(),
            nextCheckpoint
        );
        if (deleteByQuery == null) {
            finalizeCheckpoint(listener);
            return;
        }
        logger.debug(
            () -> format(
                "[%s] Run delete based on retention policy using dbq [%s] with query: [%s]",
                getJobId(),
                deleteByQuery,
                deleteByQuery.getSearchRequest()
            )
        );
        getStats().markStartDelete();
        doDeleteByQuery(deleteByQuery, ActionListener.wrap(bulkByScrollResponse -> {
            logger.trace(() -> format("[%s] dbq response: [%s]", getJobId(), bulkByScrollResponse));