Disable the query cache by default.

The query cache trades heap for faster queries. Given all the progress
that has been made on making uncached queries faster
(`IndexOrDocValuesQuery`, bitset encoding of blocks of postings, etc.),
it's not obviously a good trade-off anymore. So I suggest that we make
it an opt-in in Lucene 11.

lucene/core/src/java/org/apache/lucene/search/IndexSearcher.java

@@ -77,7 +77,8 @@
 public class IndexSearcher {
 
   static int maxClauseCount = 1024;
-  private static QueryCache DEFAULT_QUERY_CACHE;
+  // Caching is disabled by default.
+  private static QueryCache DEFAULT_QUERY_CACHE = null;
   private static QueryCachingPolicy DEFAULT_CACHING_POLICY = new UsageTrackingQueryCachingPolicy();
   private QueryTimeout queryTimeout = null;
   // partialResult may be set on one of the threads of the executor. It may be correct to not make
@@ -86,13 +87,6 @@ public class IndexSearcher {
   // shouldn't hurt either.
   private volatile boolean partialResult = false;
 
-  static {
-    final int maxCachedQueries = 1000;
-    // min of 32MB or 5% of the heap size
-    final long maxRamBytesUsed = Math.min(1L << 25, Runtime.getRuntime().maxMemory() / 20);
-    DEFAULT_QUERY_CACHE = new LRUQueryCache(maxCachedQueries, maxRamBytesUsed);
-  }
-
   /**
    * By default, we count hits accurately up to 1000. This makes sure that we don't spend most time
    * on computing hit counts