Some devices still use MCT as their UART protocol, so
we need to bring it forward to the fresh new HAL.
Also, adding tests for H4 while I'm here.
Test: new unit tests pass and a device using MCT now
boots BT again \o/
Fixes: 34992730
Change-Id: Idb8e536a2779929ad8a0d4bac492c3011995cd79