[lib/native] introduce handling Tunnelbroker peer-to-peer messages

Summary:
This adds:

1. Types od messages which is sent as payload of MessageToDevice between peers
2. Validators
3. Allow Tunnelbroker socket to call handler specific for platform

Depends on D10378

Test Plan: Tested in next diffs and end-to-end in [link to diff]

Reviewers: marcin, varun, michal

Reviewed By: michal

Subscribers: ashoat, tomek

Differential Revision: https://phab.comm.dev/D10379