ImageDrawables should be able to report errors

[rfuest]

For compressed images it isn't always possible to detect errors without actually decompressing the image. But an implementation of ImageDrawable can only forward errors caused by the DrawTarget and not generate other errors while an image is drawn. This means that the application isn't able to detect there type corrupted images and, for example, draw an broken image icon to notify the user.

[jamwaffles]

Would an enum like the following be a sensible solution?

enum ImageDrawError<E> {
    Display(DrawTarget::Error),
    Image(E)
}

and, for example, draw an broken image icon to notify the user.

Mainly thinking out loud here: This is an interesting edge case if only DrawTarget::Errors are returned; an image was drawn to the display but there was still an error, so it reinforces the need to return image-centric errors too.

[rfuest]

Would an enum like the following be a sensible solution?

Yes, but this will also need some changes in other parts of e-g, because Drawables can also only return DrawTarget errors. So this change should be part of the API overhaul to fix things like #613, perhaps making Drawables object safe, consider supporting DMA/async, alpha blending, ...