### 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
new KeyedFilter("k", new RangeQueryBuilder("test").from("2020-01-01").to("2020-02-01"))
        );
        withAggregator(builder, topLevelQuery, iw -> {
            /*
             * There has to be a document inside the query and one outside
             * the query or we'll end up with MatchAll or MathNone.
             */
            long time = DateFieldMapper.DEFAULT_DATE_TIME_FORMATTER.parseMillis("2010-01-02");
            iw.addDocument(List.of(new LongPoint("test", time), new SortedNumericDocValuesField("test", time)));
            time = DateFieldMapper.DEFAULT_DATE_TIME_FORMATTER.parseMillis("2020-01-02");
            iw.addDocument(List.of(new LongPoint("test", time), new SortedNumericDocValuesField("test", time)));
            time = DateFieldMapper.DEFAULT_DATE_TIME_FORMATTER.parseMillis("2020-01-01");
            iw.addDocument(List.of(new LongPoint("test", time), new SortedNumericDocValuesField("test", time)));
            time = DateFieldMapper.DEFAULT_DATE_TIME_FORMATTER.parseMillis("2020-02-01");
            iw.addDocument(List.of(new LongPoint("test", time), new SortedNumericDocValuesField("test", time)));
        }, (searcher, aggregator) -> {
            /*
             * The topLevelQuery is entirely contained within the filter query so
             * it is good enough to match that. See MergedPointRangeQueryTests for
             * tons more tests around this. Really in this test we're just excited
             * to prove that we unwrapped the IndexOrDocValuesQuery that the date
             * field mapper adds
             */
            QueryToFilterAdapter filter = ((FiltersAggregator) aggregator).filters().get(0);
            assertThat(filter.query(), equalTo(((IndexOrDocValuesQuery) topLevelQuery).getIndexQuery()));
            Map<String, Object> debug = new HashMap<>();
            filter.collectDebugInfo(debug::put);
            assertMap(debug, matchesMap().extraOk().entry("query", ((IndexOrDocValuesQuery) topLevelQuery).getIndexQuery().toString()));
        }, ft);
    }