Push down multi-update into StorageD

[JackChuengQAQ]

Introduction

I am the contributor of Enable MULTIUPDATE and LOOKUP | UPDATE #5953, in the current commit, graphD need to send multiple RPC request to StorageD, which may cause highly communication cost.

Contents

I am going to enhance the code, push down the multi-update into StorageD, which allows only one RPC request for multi-update.

My plan is simply described as follows. First, change the RPC Request to allow sending a set of vertex (edge) to StorageD. Second, change class UpdateVertexProcessor (UpdateEdgeProcessor) as well as UpdateTagNode (UpdateEdgeNode) to support update a bacth of vertices (edges) at a time.

If you have any advice, please let me know!