Add function to convert a texture to Standard Swizzle and vice versa

DirectXTex should add a function to convert between ``D3D12_TEXTURE_LAYOUT_ROW_MAJOR`` and ``D3D12_TEXTURE_LAYOUT_64KB_STANDARD_SWIZZLE``.

https://learn.microsoft.com/en-us/windows/win32/direct3d12/default-texture-mapping