[dxva] decoder improvements.
[dxva] Prefer the VC1_D2010 decoder over the older variant.
[dxva] removed unnecessary reinitialization of decoder.
[dxva] Optimize decoder reuse.
[dxva] don't store aligned width/height into video description.
[dxva] fill the surfaces in black, to avoid the "green screen" in case the first frame fails to decode.
[dxva] keep a reference to the d3d surface and decoder while them used by the decoder