Added ffmpeg cpu benchmark based on @nharris-lmg commands
3 options for encode (h264, av1, h265)
will report final vmaf score as "score" in report json
logs saved to artifacts
this is a ford of jd/harness-fixes that is currently live on the
benches, the ONLY thing i changed is im rounding the timestamps to the
nearest second
please approve
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Co-authored-by: J-Doiron <139803019+J-Doiron@users.noreply.github.com>