Fix percolator highlight sub fetch phase to not highlight query twice (#26622)

* Fix percolator highlight sub fetch phase to not highlight query twice

The PercolatorHighlightSubFetchPhase does not override hitExecute and since it extends HighlightPhase the search hits
are highlighted twice (by the highlight phase and then by the percolator). This does not alter the results, the second highlighting
just overrides the first one but this slow down the request because it duplicates the work.

Author: jimczi

docs/reference/search/request/highlighting.asciidoc

@@ -510,7 +510,7 @@ Response:
                 },
                 "highlight": {
                     "message": [
-                        "some message with the <em>number</em> <em>1</em>"
+                        " with the <em>number</em> <em>1</em>"
                     ]
                 }
             }

modules/percolator/src/main/java/org/elasticsearch/percolator/PercolatorHighlightSubFetchPhase.java

@@ -50,10 +50,11 @@
  * Highlighting in the case of the percolate query is a bit different, because the PercolateQuery itself doesn't get highlighted,
  * but the source of the PercolateQuery gets highlighted by each hit containing a query.
  */
-public final class PercolatorHighlightSubFetchPhase extends HighlightPhase {
+final class PercolatorHighlightSubFetchPhase implements FetchSubPhase {
+    private final HighlightPhase highlightPhase;
 
-    public PercolatorHighlightSubFetchPhase(Settings settings, Map<String, Highlighter> highlighters) {
-        super(settings, highlighters);
+    PercolatorHighlightSubFetchPhase(Settings settings, Map<String, Highlighter> highlighters) {
+        this.highlightPhase = new HighlightPhase(settings, highlighters);
     }
 
 
@@ -97,8 +98,8 @@ public void hitsExecute(SearchContext context, SearchHit[] hits) {
                         percolatorLeafReaderContext, 0, percolatorIndexSearcher
                 );
                 hitContext.cache().clear();
-                super.hitExecute(subSearchContext, hitContext);
-                hit.highlightFields().putAll(hitContext.hit().getHighlightFields());
+                highlightPhase.hitExecute(subSearchContext, hitContext);
+                hit.getHighlightFields().putAll(hitContext.hit().getHighlightFields());
             }
         }
     }