... and remove unused start, stop method from subclass.
Current implementation does not require subclass specific behavior
for the handle_frame() method.
Use consistent memory layout between dxva and other shader use case.
For example, use DXGI_FORMAT_NV12 texture format instead of
two textures with DXGI_FORMAT_R8_UNORM and DXGI_FORMAT_R8G8_UNORM.
This reverts commit ddd13fc7c0
Dynamic usage can reduce the number of copy per frame but make
things complicated and the benefit seems to not significant.
Also since we don't provide _map() method for the dynamic usage,
application cannot read buffers which make "last-sample" property
unusable in case of d3d11videosink.
Although the target platform of D3D11 decoding API are both desktop and UWP app,
DXVA header is blocked by "WINAPI_FAMILY_PARTITION(WINAPI_PARTITION_DESKTOP)"
which is meaning that that's only for desktop app.
To workaround this inconsistent annoyingness, we need to define WINAPI_PARTITION_DESKTOP
regardless of target WinAPI partition.
