### Description

It'd be lovely is a `filters` or `filter` agg that touches a `constant_keyword` would properly rewrite itself to `match_all` and `match_none` and "go fast", at least when it's at the root of the aggs tree. Theoretically it should "just work" but it doesn't seem to. Also! The `terms` agg should be able to act on there being only a single possible value. Maybe it can even act on the `match_all`/`match_none` nature of the `constant_keyword`. I'm not sure how, but it does feel like there are optimizations in there. Particularly when `terms` is the top level agg.
server/src/test/java/org/elasticsearch/search/aggregations/bucket/filter/FiltersAggregatorTests.java
FieldNamesFieldMapper.FieldNamesFieldType fnft = FieldNamesFieldMapper.FieldNamesFieldType.get(false);
        String start = "2010-01-02T00:00:00.000Z";
        String middle = "2010-01-02T00:00:05.000Z";
        String mostly = "2010-01-02T00:00:09.000Z";
        String end = "2010-01-02T00:00:10.000Z";
        CheckedConsumer<RandomIndexWriter, IOException> buildIndex = iw -> {
            long date = DateFieldMapper.DEFAULT_DATE_TIME_FORMATTER.parseMillis(start);
            long endDate = DateFieldMapper.DEFAULT_DATE_TIME_FORMATTER.parseMillis(end);
            while (date < endDate) {
                iw.addDocument(List.of(new LongPoint("test", date), new SortedNumericDocValuesField("test", date)));
                date += 100;
            }
        };
        AggregationBuilder builder = new FiltersAggregationBuilder(
            "test",
            new KeyedFilter("q1", new BoolQueryBuilder().filter(new RangeQueryBuilder("test").from(start).to(middle)))
        );
        debugTestCase(
            builder,
            LongPoint.newRangeQuery(
                "test",
                DateFieldMapper.DEFAULT_DATE_TIME_FORMATTER.parseMillis(start),
                DateFieldMapper.DEFAULT_DATE_TIME_FORMATTER.parseMillis(mostly)
            ),
            buildIndex,
            (InternalFilters filters, Class<? extends Aggregator> impl, Map<String, Map<String, Object>> debug) -> {
                assertThat(filters.getBuckets(), hasSize(1));
                assertThat(filters.getBucketByKey("q1").getDocCount(), equalTo(51L));
                assertThat(impl, equalTo(FilterByFilterAggregator.class));
                assertMap(