FEATURE: Add CompletableFuture BTree insert/get API

Author: oliviarla

src/main/java/net/spy/memcached/ArcusClient.java

@@ -3243,6 +3243,10 @@ private CollectionOperationStatus toCollectionOperationStatus(OperationStatus st
     }
   }
 
+  public Transcoder<Object> getCollectionTranscoder() {
+    return collectionTranscoder;
+  }
+
   /**
    * Get the client version.
    *