Fix bug in weight computation for query cache

When proportioning the shared RAM bytes across the shards of the query
cache, there's a computation that shares these bytes according to the
relative size of the shard cache to the total size of all the shard
caches. This computation had a bug where integer division was performed
instead which leads to this computation often being zero. This commit
fixes this bug by casting the numerator to a double before doing the
division so that double division is performed.

Relates #24856

core/src/main/java/org/elasticsearch/indices/IndicesQueryCache.java

@@ -103,7 +103,7 @@ public class IndicesQueryCache extends AbstractComponent implements QueryCache,
         }
         final double weight = totalSize == 0
                 ? 1d / stats.size()
-                : shardStats.getCacheSize() / totalSize;
+                : ((double) shardStats.getCacheSize()) / totalSize;
         final long additionalRamBytesUsed = Math.round(weight * sharedRamBytesUsed);
         shardStats.add(new QueryCacheStats(additionalRamBytesUsed, 0, 0, 0, 0));
         return shardStats;