[examples/advanced_diffusion_training] bug fixes and improvements for LoRA Dreambooth SDXL advanced training script (#5935)
* imports and readme bug fixes
* bug fix - ensures text_encoder params are dtype==float32 (when using pivotal tuning) even if the rest of the model is loaded in fp16
* added pivotal tuning to readme
* mapping token identifier to new inserted token in validation prompt (if used)
* correct default value of --train_text_encoder_frac
* change default value of --adam_weight_decay_text_encoder
* validation prompt generations when using pivotal tuning bug fix
* style fix
* textual inversion embeddings name change
* style fix
* bug fix - stopping text encoder optimization halfway
* readme - will include token abstraction and new inserted tokens when using pivotal tuning
- added type to --num_new_tokens_per_abstraction
* style fix
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Co-authored-by: Linoy Tsaban <linoy@huggingface.co>