### 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/RetentionPolicyToDeleteByQueryRequestConverter.java
throw new RetentionPolicyException("unsupported retention policy of type [{}]", retentionPolicyConfig.getWriteableName());
        }
        /* other dbq options not set and why:
         * - timeout: we do not timeout for search, so we don't timeout for dbq
         * - batch size: don't use max page size search, dbq should be simple
         */
        request.setSlices(AbstractBulkByScrollRequest.AUTO_SLICES)
            .setBatchSize(AbstractBulkByScrollRequest.DEFAULT_SCROLL_SIZE)
            
            .setAbortOnVersionConflict(false)
            
            .setRefresh(true)
            
            .setMaxRetries(0)
            .indices(destConfig.getIndex());
        
        if (settingsConfig.getDocsPerSecond() != null) {
            request.setRequestsPerSecond(settingsConfig.getDocsPerSecond());
        }
        return request;
    }
    private static QueryBuilder getDeleteQueryFromTimeBasedRetentionPolicy(
        TimeRetentionPolicyConfig config,
        TransformCheckpoint checkpoint
    ) {
        Instant cutOffDate = Instant.ofEpochMilli(checkpoint.getTimestamp()).minusMillis(config.getMaxAge().getMillis());
        return QueryBuilders.rangeQuery(config.getField()).lt(DATE_FORMATER.format(cutOffDate)).format(DATE_FORMAT);
    }
}