What does this PR do?

support AutoPipelineForText2Audio for ext2Audio model

import torch
import soundfile as sf
from diffusers import AutoPipelineForText2Audio

pipeline = AutoPipelineForText2Audio.from_pretrained(
    "stabilityai/stable-audio-open-1.0",
    torch_dtype=torch.float16
)
pipeline = pipeline.to("cuda")

output = pipeline(
    "Generate a male voice reading a paragraph",
    num_inference_steps=20,
    audio_end_in_s=10.0,
)

audio = output.audios[0].T.float().cpu().numpy()
sf.write("audio.wav", audio, pipeline.vae.sampling_rate)

audio.wav

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