[lib] improve naming in Tunnelbroker socket

Summary:
ENG-8621.

sendMessage -> sendMessageToDevice: this method is used with TunnelbrokerClientMessageToDevice prop which is device specific, alternatively this can be sendMessageToPeer
sendMessageToDeviceRequest -> sendMessage: this is a generic method interacting with raw socket and promise abstraction, alternatively sendMessageRequest

Depends on D12857

Test Plan: Just rename, yarn flow:all

Reviewers: bartek, tomek

Reviewed By: tomek

Subscribers: ashoat

Differential Revision: https://phab.comm.dev/D12858