[wip] Higgs quantization

[sayakpaul]

What does this PR do?

Testing code:

from diffusers import DiffusionPipeline, AutoModel
from diffusers.quantizers.quantization_config import HiggsConfig
import torch 

ckpt_id = "black-forest-labs/FLUX.1-dev"
transformer = AutoModel.from_pretrained(
    ckpt_id, 
    subfolder="transformer", 
    quantization_config=HiggsConfig(modules_to_not_convert=["x_embedder"]), 
    torch_dtype=torch.bfloat16,
    device_map="cuda"
)
pipe = DiffusionPipeline.from_pretrained(
    ckpt_id, 
    transformer=transformer,
    torch_dtype=torch.bfloat16
).to("cuda")

pipe_kwargs = {
    "prompt": "A cat holding a sign that says hello world",
    "height": 1024,
    "width": 1024,
    "guidance_scale": 3.5,
    "num_inference_steps": 28,
    "max_sequence_length": 512,
    "generator": torch.manual_seed(0),
}
image = pipe(**pipe_kwargs).images[0]
image.save("higgs.png")

Cc: @SunMarc @Mekkcyber

[HuggingFaceDocBuilderDev]

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[sayakpaul]

Gently pinging @SunMarc @MekkCyber now that the big OSS release is done.