Add a standard method for handling exception in Airframe RPC.

Server side

• Throw an RPCException in RPC implementations using RPCStatus code airframe-rpc: Add RPC status code #1973
• airframe-http needs to send RPCException to clients
  • finagle: embed RPCException to the HTTP response body airframe-http-finagle: Propagate RPCException to clients #2141
  • gRPC: embed RPCException to the trailer airframe-grpc: Propagate RPCException to clients #2139

Client side

• sbt-airframe should add a wrapper to convert the server side exception to RPCException airframe-rpc: Generate RPC clients based on Sync/AsyncClient  #2166
• Introduce RPCHttpClient interface in order to consolidate error handling Add RPCHttpClient to handle RPCException at client side #2165
• http client side logging to record RPCException, which will be automatically retried airframe-rpc: Client side logging #2142 airframe-grpc: Log response time and status code  #1820
• Read RPCException message from gRPC trailer