Add community video inpainting pipeline with temporal reuse

[Aki-07]

What does this PR do?

This PR introduces a new community pipeline named VideoInpaintPipeline, which extends the existing StableDiffusionInpaintPipeline to support temporally-coherent video inpainting. The pipeline allows users to perform text-guided video editing and inpainting while maintaining temporal consistency across frames, enabling realistic motion, stable lighting, and coherent textures even on mid-tier GPUs.

It achieves this by:

• Reusing diffusion noise and latent representations across consecutive frames
• Optionally applying optical-flow-guided warping (RAFT) for motion-aware latent propagation
• Adding batched FP16 inference, torch.compile acceleration, and streaming video I/O
• Providing a clean, high-level API consistent with other Diffusers pipelines

Fixes #12477

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Who can review?

@asomoza