Many functions returned void and were assumed to always succeed, and some functions
returned only a bool to indicate vague success/failure.
Now that these functions get piped over IPC all of them have to be able to indicate
an IPC failure like for example an unreachable service.
With the xrt_result_t return type they now have the opportunity to report various
types of failures.
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 fixes a regression introduced by the IPC and layer rendering
patchsets and passes the array_index to the correct places, so the
correct VkImageView is used instead of the one with index 0.
Make the renderer and IPC aware of multiple projection and quad layers
using the layer renderer.
Remove redundant code related to idle images and imported buffers and
command buffer rebuild, since we now always just display the layer
renderer's frame buffer.
Get view and projection properties from xrt_device.
Do wait on device idle when destroying the swap chain.
Don't wait on device idle multiple times in resize.
Validation on NVIDA and AMD is happy when only keeping
the two idles when resizing and destroying the swapchain.
Use the same counter for frame and command buffers, as their number is
equal, which is retrieved from swapchain.image_count.
Use the struct member num_buffers in favor of passing it as parameter.
Reuse some command buffer functions.
Create code file for common direct mode code.
Make common functions take generic parameters.
Use common code in randr and nvidia back ends.
Remove redunant includes.
In favor of own struct to determine best available mode.
The loop now also starts as one, as we do not need compare the 0th mode
it itself and returns if there is only one mode.
