Add (Scheduled) Pseudo-Huber Loss training scripts to research projects (#7527)
* add scheduled pseudo-huber loss training scripts
See #7488
* add reduction modes to huber loss
* [DB Lora] *2 multiplier to huber loss cause of 1/2 a^2 conv.
pairing of https://github.com/kohya-ss/sd-scripts/pull/1228/commits/c6495def1fbbaf2a0233110d50f976ed61620e83
* [DB Lora] add option for smooth l1 (huber / delta)
Pairing of https://github.com/kohya-ss/sd-scripts/pull/1228/commits/dd22958caa56e4db885324f76188c13bdf504569
* [DB Lora] unify huber scheduling
Pairing of https://github.com/kohya-ss/sd-scripts/pull/1228/commits/19a834c3ab448614e8887b07f2bb4e0aaabf0805
* [DB Lora] add snr huber scheduler
Pairing of https://github.com/kohya-ss/sd-scripts/pull/1228/commits/47fb1a68547e76f33cd54a3da8d2c35b9489c56e
* fixup examples link
* use snr schedule by default in DB
* update all huber scripts with snr
* code quality
* huber: make style && make quality
---------
Co-authored-by: Sayak Paul <spsayakpaul@gmail.com>