Schedule (semi-)static resource upload at converter creation time.
And use single resource for all vertex, index, and constant
buffers, since separate resources will waste GPU memory.
Note that size and address of a committed resource are 64K aligned
even if requested buffer size is small.
Part-of: <https://gitlab.freedesktop.org/gstreamer/gstreamer/-/merge_requests/7081>
Ideally, GPU waiting should be scheduled just before executing command list.
But handling the case outside of converter is a bit complicated.
Under an assumption that constructed command list will be executed
immediately, schedules GPU-side waiting inside of conversion method
to simplify the flow.
Part-of: <https://gitlab.freedesktop.org/gstreamer/gstreamer/-/merge_requests/6749>
