Introduce Converting of ID3D11Texture2D to OpenGL textures

[valbok]

OpenGL does not support NV12 textures natively, so
we should return 2 textures: for Y and UV planes.
Need to copy planes to specific texture:

1. DXGI_FORMAT_NV12 cannot be used in wglDXRegisterObjectNV
2. Creating few ID3D11Texture2D and copying the data to it
   via CopySubresourceRegion(nv12Texture) is not allowed.

Solution:

1. Create 2 shared ID3D11Texture2D textures: R8 and BGRA (not R8G8)
2. Create Shader Resource Views (SRV): R8 and R8G8
3. Create Unordered Access Views (UAV) for ID3D11Texture2D textures: plane 0 and plane 1
4. Extract planes in HLSL and copy to ID3D11Texture2D: R8 and BGRA
   NOTE: BGRA (and not R8G8) is needed by OpenGL shader used to render in QAVWidget_OpenGL
5. Generate OpenGL textures and bind ID3D11Texture2D R8 and BGRA to OpenGL via wglDXRegisterObjectNV