SystemUI: Add USB Tether tile

Co-authored-by: Björn Lundén <blunden2@gmail.com>
Co-authored-by: Bruno Martins <bgcngm@gmail.com>
Co-authored-by: Gabriele M <moto.falcon.git@gmail.com>
Co-authored-by: Luca Stefani <luca.stefani.ge1@gmail.com>
Co-authored-by: Michael Bestas <mkbestas@gmail.com>
Change-Id: Ibbc0ba9de2cc3eee2a7f6a9c9f005730244f0b3a