### Description

We have had this longstanding issue that running a top-level `filter` aggregation is often (not always, e.g. not if you need the total hit count too) a performance bug, as Elasticsearch would iterate over docs that match the `query` and would then check each of these docs against the filter of the `filter` aggregation. It's usually a better idea to put the filter directly into the query, where it can be used to drive iteration if appropriate.

We could do this automatically by implementing the `LeafCollector#competitiveIterator` API that was introduced for dynamic pruning, in order to automatically start intersecting the query with the filter of the `filter` aggregator once enough hits have been counted.
server/src/main/java/org/elasticsearch/search/aggregations/bucket/filter/FiltersAggregator.java
import org.elasticsearch.search.aggregations.Aggregator;
import org.elasticsearch.search.aggregations.AggregatorFactories;
import org.elasticsearch.search.aggregations.CardinalityUpperBound;
import org.elasticsearch.search.aggregations.InternalAggregation;
import org.elasticsearch.search.aggregations.InternalAggregations;
import org.elasticsearch.search.aggregations.LeafBucketCollector;
import org.elasticsearch.search.aggregations.LeafBucketCollectorBase;
import org.elasticsearch.search.aggregations.bucket.BucketsAggregator;
import org.elasticsearch.search.aggregations.bucket.DocCountProvider;
import org.elasticsearch.search.aggregations.support.AggregationContext;
import org.elasticsearch.xcontent.ParseField;
import org.elasticsearch.xcontent.ToXContentFragment;
import org.elasticsearch.xcontent.XContentBuilder;
import java.io.IOException;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.Objects;
import java.util.function.BiConsumer;
import java.util.function.IntPredicate;
import java.util.function.LongPredicate;
/**
 * Aggregator for {@code filters}. There are two known subclasses,
 * {@link FilterByFilterAggregator} which is fast but only works in some cases and
 * {@link Compatible} which works in all cases.
 * {@link FiltersAggregator#build} will build the fastest version that
 * works with the configuration.
 */
public abstract class FiltersAggregator extends BucketsAggregator {