Current grpc happens to be concurrent, while the grpc gateway itself is not, since it always uses abci query. Therefore, as the current queries are not concurrent, throughput has the room for improvement. This PR changes the grpc gateway so that when server is ran by a node daemon, it directly calls grpc to make queries concurrent. Any services that uses grpc gateway could improve throughput by fundamental amount, which has been tested and ensured in the process of running an Osmosis node using the current chagnes.

The code base has the following changes:
- GRPCClient field has been added to Client Context.
- The `Invoke` method in Client Context would use ABCI query when GRPCClient field is set to nil, otherwise use the GRPC Client to return results that have used grpc.
- If GRPC is set to enable in `startInProcess`, it sets the GRPC Client field in Client Context.