Fix seed-dependent failure in TestForceNoBulkScoringQuery (#16369)

The sanity check added in #16350 assumes that searching the un-wrapped
ThrowsOnBulkScoreQuery always calls ScorerSupplier#bulkScorer. With
newSearcher(reader) the searcher may be an AssertingIndexSearcher,
whose ScorerSupplier sometimes builds the bulk scorer from scorer()
instead of delegating, so the expected AssertionError is never thrown:

  gradlew -p lucene/monitor test --tests TestForceNoBulkScoringQuery \
    -Dtests.seed=BDD18A3ADD885193

Use a plain IndexSearcher so the dispatch under test is deterministic.

Author: jeho-rpls

lucene/monitor/src/test/org/apache/lucene/monitor/TestForceNoBulkScoringQuery.java

@@ -94,7 +94,10 @@ public void testBulkScoringIsDisabled() throws IOException {
       iw.commit();
 
       try (IndexReader reader = DirectoryReader.open(dir)) {
-        IndexSearcher searcher = newSearcher(reader);
+        // use a plain searcher: newSearcher may wrap with AssertingIndexSearcher, whose
+        // ScorerSupplier sometimes builds the bulk scorer from scorer() instead of delegating to
+        // bulkScorer(), which breaks the sanity check below for some seeds
+        IndexSearcher searcher = new IndexSearcher(reader);
         // disable query caching, so that we exercise the search path directly rather than
         // any bulk-scoring optimizations the cache may apply internally
         searcher.setQueryCache(null);