Fix channel format when padding non-square images for certain models

[xenova]

This PR fixes a bug encountered when padding non-square images for swin2sr-like models. It also adds support for the new APISR super-resolution models.

Example: Upscale an image with Xenova/4x_APISR_GRL_GAN_generator-onnx.

import { pipeline } from '@xenova/transformers';

// Create image-to-image pipeline
const upscaler = await pipeline('image-to-image', 'Xenova/4x_APISR_GRL_GAN_generator-onnx', {
    quantized: false,
});

// Upscale an image
const url = 'https://huggingface.co/datasets/Xenova/transformers.js-docs/resolve/main/anime.png';
const output = await upscaler(url);
// RawImage {
//   data: Uint8Array(16588800) [ ... ],
//   width: 2560,
//   height: 1920,
//   channels: 3
// }

// (Optional) Save the upscaled image
output.save('upscaled.png');

See example output

Input image:

Output image:

[HuggingFaceDocBuilderDev]

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