[Feat] Add LensPipeline （microsoft/Lens）

[RuixiangMa]

What does this PR do?

Add support for Lens , text-to-image models from Microsoft.
Repoid: microsoft/Lens

import torch
from diffusers import LensPipeline

pipe = LensPipeline.from_pretrained("microsoft/Lens", torch_dtype=torch.bfloat16)
pipe.to("cuda")

prompt = "A steampunk floating sky-city built on massive gear-driven platforms, 
brass and copper towers connected by chain bridges, steam-powered airships and 
hot air balloons docking at various levels, sunset clouds below the city, detailed concept art"
generator = torch.Generator("cuda").manual_seed(42)
image = pipe(prompt, height=1440, width=1440, num_inference_steps=20, guidance_scale=5.0, generator=generator).images[0]
image.save("lens.png")

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