[proto][Tunnelbroker] add RPC to delete device data from Tunnelbroker

Summary:
ENG-8400 (see point 5. Logout).

This RPC will be used by Identity to inform Tunnelbroker about device logout.

Now remove the device token. Creating a follow-up task to delete persisted messages to device (ENG-8495).

Test Plan: Tested in next diff

Reviewers: bartek, marcin, ashoat

Reviewed By: bartek, ashoat

Subscribers: tomek

Differential Revision: https://phab.comm.dev/D12525