Add image selection from server in the Photo Manager (the expanded view accessible from the carousel)

[teolemon]

What

• Photos already on the server, and selected for a purpose (eg ingredients) contain valuable info (like a nutrition table)
• Create a view listing all the images available for a product server-side
• Make this view reusable in the photo picker

Part of

• Improve the Photo Manager using new features from openfoodfacts-dart #766

[monsieurtanuki]

Waiting for openfoodfacts/openfoodfacts-dart#689 to be reviewed.

This is what it will look like:

A bit similar to what @VaiTon implemented in #2724, but now we make a strict distinction between the 4 main images (in one page) and the bulk of uploaded images (in a specific page).

[monsieurtanuki]

I must say that it works very well and that of course the server answers quickly - here we don't upload anything, we just crop an existing image.