Add RPC sender tracing

We currently have RPC tracing on the receiver side, but not on the the sender side. For slow RPCs, the logs print out the total amount of time spent sending the RPC + the network time. Adding tracing will basically make this more granular. It will help determine where exactly in the stack the time was spent when sending RPCs.

Combined with the trace logs in the receiver, it should be much easier to determine the timeline of a given slow RPC.