direct3d11: use a ID3D11Fence to tell when the rendering is done
This is a lot more accurate and wastes a lot less time than the Query approach. The D3D11 Fence value is set when the GPU is done doing the previous (rendering) commands. Then we can wait in the CPU for this event and return when it's done. All decoder/filter commands seem to not have any impact so that's really the signal we're looking for to tell the core we're done rendering. This is only supported on newer mingw toolchains and only on Windows 10 Creators Update, which should cover pretty much all Win10 installed machines. Better fixes #21600
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