PremultipliedImage/UnassociatedImage: Add support for different backing storage

[kkaefer]

On Android, we're currently copying over the pixels from the underlying Android Bitmap when we initialize an Image. Instead, we should change our Image implementation on Android so that it always uses java Bitmap object as the backing store to avoid converting back and forth.

/cc @asheemmamoowala

[asheemmamoowala]

Android P introduces a replacement for BitmapFactory that may help with this: ImageDecoder

[kkaefer]

Great, that means we can switch over once 2024 rolls around :)

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This issue has been automatically detected as stale because it has not had recent activity and will be archived. Thank you for your contributions.

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This issue has been automatically detected as stale because it has not had recent activity and will be archived. Thank you for your contributions.

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This issue has been automatically detected as stale because it has not had recent activity and will be archived. Thank you for your contributions.