Product is not useable on Plone 6

[laulaz]

Beside #129, we have another big problem with OOTB Plone 6.

Most of the new image scales (introduced here) use 65536 as maximum height, see https://github.com/plone/plone.base/blob/38fe6d57faf9185f91b418a54bdff725ecb9f242/src/plone/base/interfaces/controlpanel.py#L1683-L1689

In plone.app.imagecropping, all of these scales are shown as not croppable, because the height can never be reached :

The product is quite useless if you keep Plone scales ...

[MrTango]

I had the same issue. But if you use a special scale, like a banner 1000x333px, which i wanted anyway it still works fine.
In the case of the very high numbers for height, we could calculate the default height from the width and aspect ratio and use this instead of complaining about the to high number.

[MrTango]

something like:

if scale_height > orig_height:
    height = calculate_height_from_orig(image) 
else:
    height = scale_height

[petschki]

this should be fixed with #144