[Tunnelbroker] add MessageID field to MessageToDevice

Summary:
Clients need to know messageID to confirm message receive.
Keeping old in commtest struct to make tests more readable.

Depends on D9571

Test Plan: Run all Tunnelbroker tests (But overall this doesn't affect logic).

Reviewers: michal, bartek, varun, jon

Reviewed By: bartek

Subscribers: ashoat, tomek, wyilio

Differential Revision: https://phab.comm.dev/D9572