Fix script score function that combines _score and weight (#22713)

The weight factor function does not check if the delegate score function needs to access the score of the query.
This results in a _score equals to 0 for all score function that set a weight.
This change modifies the WeightFactorFunction#needsScore to delegate the call to its underlying score function.

Fix #21483

core/src/main/java/org/elasticsearch/common/lucene/search/function/WeightFactorFunction.java

@@ -68,7 +68,7 @@ public class WeightFactorFunction extends ScoreFunction {
 
     @Override
     public boolean needsScores() {
-        return false;
+        return scoreFunction.needsScores();
     }
 
     public Explanation explainWeight() {

core/src/test/java/org/elasticsearch/index/query/functionscore/FunctionScoreTests.java

@@ -751,6 +751,33 @@ public class FunctionScoreTests extends ESTestCase {
         assertThat(searchResult.scoreDocs[0].score, equalTo(explanation.getValue()));
     }
 
+    public void testWeightFactorNeedsScore() {
+        for (boolean needsScore : new boolean[] {true, false}) {
+            WeightFactorFunction function = new WeightFactorFunction(10.0f, new ScoreFunction(CombineFunction.REPLACE) {
+                @Override
+                public LeafScoreFunction getLeafScoreFunction(LeafReaderContext ctx) throws IOException {
+                    return null;
+                }
+
+                @Override
+                public boolean needsScores() {
+                    return needsScore;
+                }
+
+                @Override
+                protected boolean doEquals(ScoreFunction other) {
+                    return false;
+                }
+
+                @Override
+                protected int doHashCode() {
+                    return 0;
+                }
+            });
+            assertEquals(needsScore, function.needsScores());
+        }
+    }
+
     private static class DummyScoreFunction extends ScoreFunction {
         protected DummyScoreFunction(CombineFunction scoreCombiner) {
             super(scoreCombiner);