[services] Tunnelbroker - Update handling of the newNotifyToken in Get stream request

Summary:
This diff introduces handling of the newNotifyToken in Get stream request.
When the device has an invalid or expired notification token we are requesting a new token from the client (ref to D5207).
The client gets back with the new token in Get stream request when starts listening for new messages (getting messages) from the Tunnelbroker.

This is a part of the stack.
This approach was used keeping in mind the transition to the bidirectional stream soon.

Related Linear task: ENG-1782 and ENG-1816

Test Plan: Successfully built the service and passed unit and integration tests.

Reviewers: jon, tomek

Reviewed By: jon, tomek

Subscribers: ashoat, tomek, atul, abosh

Differential Revision: https://phab.comm.dev/D5206