This change adds an aggregation that can be used to delay the
query phase execution on shards with a configurable time:

{
    "aggs": {
        "delay": {
            "shard_delay": {
                "value": "30s"
            },
            "aggs": {
                "host": {
                    "terms": {
                        "field": "hostname"
                    }
                }
            }
        }
    }
}

This test module is built on top of elastic#61954 so the aggregation will be available only within
snapshots since this module is not meant to be used in production.

Closes elastic#54159