Refactor: support image extraction

[christinestraub]

Summary

This PR is the second part of the "image extraction" refactor to move it from unstructured-inference repo to unstructured repo, the first part is done in Unstructured-IO/unstructured-inference#299. This PR adds logic to support extracting images.

Testing

git clone -b refactor/remove_image_extraction_code --single-branch https://github.com/Unstructured-IO/unstructured-inference.git && cd unstructured-inference && pip install -e . && cd ../

elements = partition_pdf(
        filename="example-docs/embedded-images.pdf",
        strategy="hi_res",
        extract_images_in_pdf=True,
    )

print("\n\n".join([str(el) for el in elements]))