adapt to ocrd v3

[bertsky]

attempt at migration towards https://github.com/OCR-D/core/pull/1240

no tests yet, I will try to add some CI here

@kba see ocrd_segment.replace_original for the use case of passing PageType in OcrdPageResultImage.images.alternative_image. – It pairs with the complementary ocrd_segment.replace_page, so one can use replace-original to rebase, then run a few steps, and then use replace-page with the result as second fileGrp and the original fileGrp as second fileGrp to continue with the results (all annotation below page level) in the original coordinate system.