Fix rollup search statistics (#36674)

This change fixes the rollup statistics regarding search times. Search times are
computed from the first query and never updated. This commit adds the missing
calls to the subsequent search.

Author: jimczi

x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/indexing/AsyncTwoPhaseIndexer.java

@@ -356,8 +356,12 @@ private void onBulkResponse(BulkResponse response, JobPosition position) {
             ActionListener<SearchResponse> listener = ActionListener.wrap(this::onSearchResponse, this::finishWithSearchFailure);
             // TODO probably something more intelligent than every-50 is needed
             if (stats.getNumPages() > 0 && stats.getNumPages() % 50 == 0) {
-                doSaveState(IndexerState.INDEXING, position, () -> doNextSearch(buildSearchRequest(), listener));
+                doSaveState(IndexerState.INDEXING, position, () -> {
+                    stats.markStartSearch();
+                    doNextSearch(buildSearchRequest(), listener);
+                });
             } else {
+                stats.markStartSearch();
                 doNextSearch(buildSearchRequest(), listener);
             }
         } catch (Exception e) {