Enable portability subset physical device enumeration.
Don't use Vulkan 1.1+ logical devices on Vulkan 1.0 instances due to the
VkApplicationInfo::apiVersion specification.
Make sure all extension dependencies are enabled when creating a device.
Prefer exposing feature support over extension support via the device
interface to avoid causing confusion with regard to promoted extensions
(especially those that required some features as extensions, but had those
features made optional when they were promoted).
Allow creating presentation-only devices, not demanding any optional
features beyond the basic Vulkan 1.0, for use cases such as internal tools
or CPU rendering.
Require the independentBlend feature for GPU emulation as working around is
complicated, while support is almost ubiquitous.
Move the graphics system initialization fatal error message to xenia_main
after attempting to initialize all implementations, for automatic fallback
to other implementations in the future.
Log Vulkan driver info.
Improve Vulkan debug message logging, enabled by default.
Refactor code, with simplified logic for enabling extensions and layers.
