Instead of maintaining this chunk of code and build options, the Vulkan
loader can be used to load up validation. This has the advantage that no
layer name needs to be hard coded inside Monado, which was subject of
change recently.
Instead of using our own environment variable we can easily set the one
from the loader, e.g. `VK_INSTANCE_LAYERS=VK_LAYER_KHRONOS_validation`.
This adds a driver for the Vive family of devices based on Philipp
Zabel's ouvrt.
The driver currently only handles the IMU and main board report streams,
but is able to acquire the JSON configuration and utilize it for IMU
calibration as well as distortion configuration.