### Description

Our most common aggregations should be optimized for single-valued fields. In general, our aggregations look like this:

```java
    @Override
    public LeafBucketCollector getLeafCollector(LeafReaderContext ctx, LeafBucketCollector sub) throws IOException {
        if (valuesSource == null) {
            return LeafBucketCollector.NO_OP_COLLECTOR;
        }
        SortedNumericDocValues values = valuesSource.longValues(ctx);
        return new LeafBucketCollectorBase(sub, values) {
            @Override
            public void collect(int doc, long owningBucketOrd) throws IOException {
                if (values.advanceExact(doc)) {
                    int valuesCount = values.docValueCount();
                    for (int i = 0; i < valuesCount; ++i) {
                        long value = values.nextValue();
                        // do something with value
                    }
                }
            }
        };
    }
```

The idea consists of optimizing for single-valued fields by unwrapping the single-valued doc-value iterator:

```java
    @Override
    public LeafBucketCollector getLeafCollector(LeafReaderContext ctx, LeafBucketCollector sub) throws IOException {
        if (valuesSource == null) {
            return LeafBucketCollector.NO_OP_COLLECTOR;
        }
        SortedNumericDocValues values = valuesSource.longValues(ctx);
        NumericDocValues singleValues = DocValues.unwrapSingleton(values); // or FieldData.unwrapSingleton for doubles
        if (singleValues != null) {
            return new LeafBucketCollectorBase(sub, values) {
                @Override
                public void collect(int doc, long owningBucketOrd) throws IOException {
                    if (singleValues.advanceExact(doc)) {
                        long value = singleValues.longValue();
                        // do something with value
                    }
                }
            };
        } else {
            return new LeafBucketCollectorBase(sub, values) {
                @Override
                public void collect(int doc, long owningBucketOrd) throws IOException {
                    if (values.advanceExact(doc)) {
                        int valuesCount = values.docValueCount();
                        for (int i = 0; i < valuesCount; ++i) {
                            long value = values.nextValue();
                            // do something with value
                        }
                    }
                }
            };
        }
    }
```

The `terms` aggregation already does this, and e.g. `min` and `max` aggregations use similar tricks that also help optimize the single-valued case. But `date_histogram`, which is one of our most common aggregations, doesn't. Let's specialize the single-value case for date histograms too?
server/src/internalClusterTest/java/org/elasticsearch/search/profile/aggregation/AggregationProfilerIT.java
.entry("results_from_metadata", 0)
                                                .entry("specialized_for", "match_all")
                                        )
                                    )
                            )
                    )
            );
        }
    }
    public void testDateHistogramFilterByFilterDisabled() throws InterruptedException, IOException {
        assertAcked(
            client().admin()
                .cluster()
                .prepareUpdateSettings()
                .setPersistentSettings(Settings.builder().put(SearchService.ENABLE_REWRITE_AGGS_TO_FILTER_BY_FILTER.getKey(), false))
        );
        try {
            assertAcked(
                client().admin()
                    .indices()
                    .prepareCreate("date_filter_by_filter_disabled")
                    .setSettings(Map.of("number_of_shards", 1, "number_of_replicas", 0))
                    .setMapping("date", "type=date", "keyword", "type=keyword")
                    .get()
            );
            List<IndexRequestBuilder> builders = new ArrayList<>();
            for (int i = 0; i < RangeAggregator.DOCS_PER_RANGE_TO_USE_FILTERS * 2; i++) {
                String date = Instant.ofEpochSecond(i).toString();
                builders.add(
                    client().prepareIndex("date_filter_by_filter_disabled")