obs-ffmpeg: Add texture-based hardware AMD encoder

Adds support for texture-based AMD encoding, with both H264, HEVC, and
HDR support. Falls back to FFmpeg when texture-based encoding cannot be
used for whatever reason.

(Jim note: This is based upon obsproject/obs-studio#4538 by AMD/Luxoft
with fewer files, FFmpeg fallback for software encoding, and HDR
support. I also went to lengths to ensure that FFmpeg command line
parameters also works with it)

Co-authored-by: Jim <obs.jim@gmail.com>