Add more H264 encoder options.
This patch set adds 4 more H264 encoding options from GStreamer:
- nvautogpuh264 (new nvenc api)
- openh264
- vulkanh264
- vaapih264
It also removes a redundant queue for GPU encoders, which improves latency by 10-20ms in the begin to decode benchmark. The old nvenc API option is left in place for older (like 2 months old) GStreamer versions.