support StableDiffusionAdapterPipeline.from_single_file

[Teriks]

What does this PR do?

Adds support for from_single_file to StableDiffusionAdapterPipeline by inheriting FromSingleFileMixin

import diffusers
from PIL import Image
from diffusers.utils import load_image
import torch

# checkpoint: https://civitai.com/api/download/models/74821?type=Model&format=SafeTensor&size=pruned&fp=fp16

image = load_image(
     "https://huggingface.co/datasets/diffusers/docs-images/resolve/main/t2i-adapter/color_ref.png"
)

color_palette = image.resize((8, 8))
color_palette = color_palette.resize((512, 512), resample=Image.Resampling.NEAREST)

adapter = diffusers.T2IAdapter.from_pretrained("TencentARC/t2iadapter_color_sd14v1", torch_dtype=torch.float16)

# single file load
pipe = diffusers.StableDiffusionAdapterPipeline.from_single_file(
    'impressionismOil_sd15.safetensors',
     adapter=adapter, torch_dtype=torch.float16)

pipe.to('cuda')

output = pipe(
    prompt='impressionist oil painting of a sunset', image=color_palette).images[0]

output.save('test.png')

Previously working around this with:

pipe_class = type(
    'StableDiffusionAdapterPipeline',  
    (diffusers.loaders.FromSingleFileMixin, diffusers.StableDiffusionAdapterPipeline), {})

Fixes #9123

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@DN6

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