Add external encoder VVenC for H266/VVC encoding.
Register new encoder libvvenc.
Add libvvenc to wrap the vvenc interface.
libvvenc implements encoder option: preset,qp,qpa,period,
passlogfile,stats,vvenc-params,level,tier.
Enable encoder by adding --enable-libvvenc in configure step.

Co-authored-by: Christian Bartnik chris10317h5@gmail.com
Signed-off-by: Thomas Siedel <thomas.ff@spin-digital.com>