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.
Even if one of downstream d3d11 elements can support dynamic-usage memory,
another one might not support it. Also, to support dynamic-usage,
both upstream and downstream d3d11device must be the same object.
In some cases, rendering and dxgi (e.g., swapchain) APIs should be
called from window message pump thread, but current design (dedicated d3d11 thread)
make it impossible. To solve it, change concurrency model to locking based one
from single-thread model.
