Update validation layer string to VK_LAYER_KHRONOS_validation.
While we are at it, properly check for available validation layers
before enabling them.
Reduces some header churn and reduces rebuilds when some header
internals change.
While we're at it we can also resolve a missing include in buffer_cache.
Render.Vulkan <Error> video_core/renderer_vulkan/renderer_vulkan.cpp:CreateInstance:131: Presentation not supported on this platform
Render.Vulkan <Error> video_core/renderer_vulkan/renderer_vulkan.cpp:CreateSurface:378: Presentation not supported on this platform
Core <Critical> core/core.cpp:Load:199: Failed to initialize system (Error 5)!
Changes the GraphicsContext to be managed by the GPU core. This
eliminates the need for the frontends to fool around with tricky
MakeCurrent/DoneCurrent calls that are dependent on the settings (such
as async gpu option).
This also refactors out the need to use QWidget::fromWindowContainer as
that caused issues with focus and input handling. Now we use a regular
QWidget and just access the native windowHandle() directly.
Another change is removing the debug tool setting in FrameMailbox.
Instead of trying to block the frontend until a new frame is ready, the
core will now take over presentation and draw directly to the window if
the renderer detects that its hooked by NSight or RenderDoc
Lastly, since it was in the way, I removed ScopeAcquireWindowContext and
replaced it with a simple subclass in GraphicsContext that achieves the
same result