A fence configured in GstD3D12Memory should be used only for
write access to be completed. And because d3d12 -> d3d11 copy path
is read access to d3d12 resource, we should not set fence to
memory. Otherwise another read access to the d3d12 resource
will wait for d3d11 device context's copy operation although
simultaneous read access is allowed.
Use background thread to keep d3d12 resource and wait for d3d11 device's
copy operation instead.
Part-of: <https://gitlab.freedesktop.org/gstreamer/gstreamer/-/merge_requests/7243>
If a d3d12 memory holds non-direct-queue fence but the fence was
created with D3D12_FENCE_FLAG_SHARED flag, use the fence instead of
waiting for fence at CPU side. Note that d3d12ipcsrc or
d3d12screencapture elements will hold such sharable fence.
Part-of: <https://gitlab.freedesktop.org/gstreamer/gstreamer/-/merge_requests/7139>
