Add unsupported parameters to HLRC search request (#53745)

Currently we don't send values for the `pre_filter_shard_size` and
`max_concurrent_shard_requests` SearchRequest parameters over http when using
the High Level Rest Client. This change adds these parameters to the
RequestConverters and tests.

client/rest-high-level/src/main/java/org/elasticsearch/client/RequestConverters.java

@@ -410,6 +410,8 @@ final class RequestConverters {
         params.withIndicesOptions(searchRequest.indicesOptions());
         params.putParam("search_type", searchRequest.searchType().name().toLowerCase(Locale.ROOT));
         params.putParam("ccs_minimize_roundtrips", Boolean.toString(searchRequest.isCcsMinimizeRoundtrips()));
+        params.putParam("pre_filter_shard_size", Integer.toString(searchRequest.getPreFilterShardSize()));
+        params.putParam("max_concurrent_shard_requests", Integer.toString(searchRequest.getMaxConcurrentShardRequests()));
         if (searchRequest.requestCache() != null) {
             params.putParam("request_cache", Boolean.toString(searchRequest.requestCache()));
         }

client/rest-high-level/src/test/java/org/elasticsearch/client/RequestConvertersTests.java

@@ -1857,6 +1857,14 @@ public class RequestConvertersTests extends ESTestCase {
             searchRequest.setCcsMinimizeRoundtrips(randomBoolean());
         }
         expectedParams.put("ccs_minimize_roundtrips", Boolean.toString(searchRequest.isCcsMinimizeRoundtrips()));
+        if (randomBoolean()) {
+            searchRequest.setMaxConcurrentShardRequests(randomIntBetween(1, Integer.MAX_VALUE));
+        }
+        expectedParams.put("max_concurrent_shard_requests", Integer.toString(searchRequest.getMaxConcurrentShardRequests()));
+        if (randomBoolean()) {
+            searchRequest.setPreFilterShardSize(randomIntBetween(2, Integer.MAX_VALUE));
+        }
+        expectedParams.put("pre_filter_shard_size", Integer.toString(searchRequest.getPreFilterShardSize()));
     }
 
     static void setRandomIndicesOptions(Consumer<IndicesOptions> setter, Supplier<IndicesOptions> getter,