Aggregation: Prune first before checking the bucket limit

[PSeitz]

"aggs": {
	"2": {
		"aggs": {
			"3": {
				"date_histogram": {
					"field": "msg_time",
					"fixed_interval": "1000ms",
					"min_doc_count": 0,
					"extended_bounds": {
						"min": 1695105266331,
						"max": 1695105566331
					}
				}
			}
		},
		"terms": {
			"field": "level",
			"size": 100,
			"order": {
				"_count": "desc"
			},
			"min_doc_count": 0
		}
	}
}, "query": {
	"bool": {
		"filter": {
			"range": {
				"msg_time": {
					"gte": "2023-09-19T06:34:26.331Z",
					"lte": "2023-09-19T06:39:26.331Z"
				}
			}
		}
	}
}, "size": 0
}

This request fails with Aborting aggregation because bucket limit was exceeded. Limit: 65000, Current: 102714.
but the number of buckets returned is 30_000 (300 date histogram bucket * 100 term buckets). Probably related to pruning after merging first, before counting the buckets.

[PSeitz]

Pruning and counting works correctly in the finalization state. The actual issue is fixed here: #2183