### 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
public void testWithMergedPointRangeQueries() throws IOException {
        MappedFieldType ft = new DateFieldMapper.DateFieldType("test", Resolution.MILLISECONDS);
        AggregationBuilder builder = new FiltersAggregationBuilder(
            "test",
            new KeyedFilter("q1", new RangeQueryBuilder("test").from("2020-01-01").to("2020-03-01").includeUpper(false))
        );
        Query query = LongPoint.newRangeQuery(
            "test",
            DateFieldMapper.DEFAULT_DATE_TIME_FORMATTER.parseMillis("2020-01-01"),
            DateFieldMapper.DEFAULT_DATE_TIME_FORMATTER.parseMillis("2020-02-01")
        );
        testCase(iw -> {
            iw.addDocument(List.of(new LongPoint("test", DateFieldMapper.DEFAULT_DATE_TIME_FORMATTER.parseMillis("2010-01-02"))));
            iw.addDocument(List.of(new LongPoint("test", DateFieldMapper.DEFAULT_DATE_TIME_FORMATTER.parseMillis("2020-01-02"))));
        }, result -> {
            InternalFilters filters = (InternalFilters) result;
            assertThat(filters.getBuckets(), hasSize(1));
            assertThat(filters.getBucketByKey("q1").getDocCount(), equalTo(1L));
        }, new AggTestConfig(builder, ft).withQuery(query));
    }
    public void testWithEmptyMergedPointRangeQueries() throws IOException {
        MappedFieldType ft = new DateFieldMapper.DateFieldType("test", Resolution.MILLISECONDS);
        AggregationBuilder builder = new FiltersAggregationBuilder(
            "test",
            new KeyedFilter("q1", new RangeQueryBuilder("test").from("2020-01-01").to("2020-02-01").includeUpper(false))
        );
        Query query = LongPoint.newRangeQuery(
            "test",
            DateFieldMapper.DEFAULT_DATE_TIME_FORMATTER.parseMillis("2010-01-01"),
            DateFieldMapper.DEFAULT_DATE_TIME_FORMATTER.parseMillis("2015-02-01")