Also make the ReadCloser an Controllable allows to uncouple
the controller implementation from the encoder.
This is not needed for the 2 codec controller already implemented (openh264 and vpx)
but is more future proof in case it required for other codecs.
Previous reference frame update sequence was borrowed from
an example in libva-utils, however the quality of the output
was not good (block noised).
This commit disables alternate frame and updates golden frame only
on keyframe. It doesn't enable full referencing feature of VP8, but
ffmpeg vaapi encoder looks also not fully using golden frame and
alternate frame.
Resolves https://github.com/pion/mediadevices/issues/114
* Remove codec registrar
* Completely redesign how codec is being discovered, tuned, and built
* Update examples
* Update unit tests
Valentin Cocaud