* Add videoprocessor feature to d3d11converter, in order to unifiy
conversion flow.
* Add convert_buffer() method to support automatic shader/videoprocessor
selection. The method also supports texture upload if input memory
cannot be used for conversion (e.g., system memory or so)
Part-of: <https://gitlab.freedesktop.org/gstreamer/gstreamer/-/merge_requests/2697>
Rewriting GstD3D11Converter (equivalent to GstVideoConverter)
to optimize some conversion path and clean up.
* Extract YUV <-> RGB conversion matrix building method to
utils. It will be used by other implementation
* Use calculated offset values for YCbCr <-> YPbPr conversion
instead of hardcoded values
* Handle color range adjustment
* Move transform matrix building helper function to utils.
The method will be used by other elements
* Use single constant buffer. Multiple constatne buffer for
conversion pipeline is almost pointless
* Remove lots of duplicated HLSL code and split pixel shader
code path into sampling -> colorspace conversion ->
shader output packing
* Avoid floating point precision error around UV coordinates
* Optimize RGB -> YUV conversion path
Part-of: <https://gitlab.freedesktop.org/gstreamer/gstreamer/-/merge_requests/2581>
