Make SearchPhaseController.reducedQueryPhase a little cheaper (elastic#97848)

Saw this one in recent profiling sessions -> remove redundant multiple
iterations of the results collection and cleanup slightly inefficient
assertion usage.

Author: original-brownbear

server/src/main/java/org/elasticsearch/action/search/SearchPhaseController.java

@@ -541,15 +541,25 @@ static ReducedQueryPhase reducedQueryPhase(
             );
         }
         int total = queryResults.size();
-        queryResults = queryResults.stream().filter(res -> res.queryResult().isNull() == false).toList();
-        String errorMsg = "must have at least one non-empty search result, got 0 out of " + total;
-        assert queryResults.isEmpty() == false : errorMsg;
-        if (queryResults.isEmpty()) {
-            throw new IllegalStateException(errorMsg);
+        final Collection<SearchPhaseResult> nonNullResults = new ArrayList<>();
+        boolean hasSuggest = false;
+        boolean hasProfileResults = false;
+        for (SearchPhaseResult queryResult : queryResults) {
+            var res = queryResult.queryResult();
+            if (res.isNull()) {
+                continue;
+            }
+            hasSuggest |= res.suggest() != null;
+            hasProfileResults |= res.hasProfileResults();
+            nonNullResults.add(queryResult);
         }
+        queryResults = nonNullResults;
         validateMergeSortValueFormats(queryResults);
-        final boolean hasSuggest = queryResults.stream().anyMatch(res -> res.queryResult().suggest() != null);
-        final boolean hasProfileResults = queryResults.stream().anyMatch(res -> res.queryResult().hasProfileResults());
+        if (queryResults.isEmpty()) {
+            var ex = new IllegalStateException("must have at least one non-empty search result, got 0 out of " + total);
+            assert false : ex;
+            throw ex;
+        }
 
         // count the total (we use the query result provider here, since we might not get any hits (we scrolled past them))
         final Map<String, List<Suggestion<?>>> groupedSuggestions = hasSuggest ? new HashMap<>() : Collections.emptyMap();
@@ -578,9 +588,7 @@ static ReducedQueryPhase reducedQueryPhase(
                     }
                 }
             }
-            if (bufferedTopDocs.isEmpty() == false) {
-                assert result.hasConsumedTopDocs() : "firstResult has no aggs but we got non null buffered aggs?";
-            }
+            assert bufferedTopDocs.isEmpty() || result.hasConsumedTopDocs() : "firstResult has no aggs but we got non null buffered aggs?";
             if (hasProfileResults) {
                 String key = result.getSearchShardTarget().toString();
                 profileShardResults.put(key, result.consumeProfileResult());