* GPU: D3D12: Missing WinPixEventRuntime.dll now logs warning at device creation time.
* GPU: D3D12: Debug label functions are now a no-op when WinPixEventRuntime.dll is missing.
* Docs: GPU: Debug function documentation now notes WinPixEventRuntime.dll is required under D3D12.
This prevents validation errors on D3D12 caused by the previous solution
that utilized internal D3D12 functions. This is still the fallback
solution if WinPixEventRuntime.dll is not present in PATH, but a warning
is printed to let you know how to fix these errors.