### 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/main/java/org/elasticsearch/search/aggregations/bucket/filter/FiltersAggregator.java
new FilterByFilterAggregator.AdapterBuilder<FilterByFilterAggregator>(
                name,
                keyed,
                keyedBucket,
                otherBucketKey,
                context,
                parent,
                cardinality,
                metadata
            ) {
                @Override
                protected FilterByFilterAggregator adapt(
                    CheckedFunction<AggregatorFactories, FilterByFilterAggregator, IOException> delegate
                ) throws IOException {
                    return delegate.apply(factories);
                }
            };
        for (QueryToFilterAdapter f : filters) {
            filterByFilterBuilder.add(f);
        }
        FilterByFilterAggregator filterByFilter = filterByFilterBuilder.build();
        if (filterByFilter != null) {
            return filterByFilter;
        }
        return new FiltersAggregator.Compatible(
            name,
            factories,
            filters,
            keyed,
            keyedBucket,