### Description

Follow-up of #98360: when there is a single filter, the collector could save the overhead of the priority queue (both in `collect()` and `competitiveIterator()`), which would likely result in a speedup.
server/src/main/java/org/elasticsearch/search/aggregations/bucket/filter/FiltersAggregator.java
import org.elasticsearch.search.aggregations.AggregationExecutionContext;
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.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 {