Makes wifi configurable over shared memory

Passes the mac addresses of host and guest devices through the wifi
exchange region.
Changes MacAddress type to std::array to make its size known at
compile time and moves it to the region view.

Test: run on gce
Bug: 76433498
Change-Id: Ie964a22424f0ff5004d32efcdf487894b8083c62
(cherry picked from commit 11aa414b)