branch to re-upstream tiktok updates from x-portrait

[johndpope]

Tiktok naturally didn't include any training code.... https://github.com/bytedance/X-Portrait

it would be good to be able to retrofit this code base with their updates... they also give up on the body animation.... they're using torch2 - i've been looking into it - but not sure if the entire model would need to be retrained....