[tunnelbroker] Close WS session when received special AMQP message

Summary:
Address ENG-8256.

Added a special AMQP message, that when received by consumer for given device ID, the websocket session is closed.

Test Plan: Modified SendMessageToDevice to send this message instead. Confirmed that the device is disconnected.

Reviewers: kamil

Reviewed By: kamil

Subscribers: ashoat, tomek

Differential Revision: https://phab.comm.dev/D13227