[HUDI-1483] Support async clustering for deltastreamer and Spark streaming (#3142)

- Integrate async clustering service with HoodieDeltaStreamer and HoodieStreamingSink
- Added methods in HoodieAsyncService to reuse code

hudi-common/src/main/java/org/apache/hudi/common/util/ClusteringUtils.java

@@ -206,4 +206,8 @@ public class ClusteringUtils {
     metrics.put(TOTAL_LOG_FILES, (double) numLogFiles);
     return metrics;
   }
+
+  public static List<HoodieInstant> getPendingClusteringInstantTimes(HoodieTableMetaClient metaClient) {
+    return metaClient.getActiveTimeline().filterPendingReplaceTimeline().getInstants().collect(Collectors.toList());
+  }
 }