[1/3]Implemente LRO Operation Callable Method sample code

[summer-ji-eng]

Inside of try body,

1. construct request with default values.
2. Assign future variable with invoking LRO callable method.
3. Assign response variable with invoking future.get method.

   * try (CloudRedisClient cloudRedisClient = CloudRedisClient.create()) {
   *   LocationName parent = LocationName.of("[PROJECT]", "[LOCATION]");
   *   String instanceId = "test_instance";
   *   Instance.Tier tier = Instance.Tier.BASIC;
   *   int memorySizeGb = 1;
   *   Instance instance = Instance.newBuilder()
   *     .setTier(tier)
   *     .setMemorySizeGb(memorySizeGb)
   *     .build();
   *   CreateInstanceRequest request = CreateInstanceRequest.newBuilder()
   *     .setParent(parent.toString())
   *     .setInstanceId(instanceId)
   *     .setInstance(instance)
   *     .build();
   *   OperationFuture<Instance, OperationMetadata> future = cloudRedisClient.createInstanceOperationCallable().futureCall(request);
   *   // Do something
   *   Instance response = future.get();
   * }

[miraleung]

Has master been merged into the base branch recently?

[summer-ji-eng]

Has master been merged into the base branch recently?

Thanks for reminding. Yes. The lastest commit from master is #604