Less magic xml conversion between poppler annotation and okular annotations

Right now we're assuming that poppler and okular store the annotations in the same exact xml format and then abusing that to call Poppler::AnnotationUtils::storeAnnotation + Okular::AnnotationUtils::createAnnotation to pass XML between them.

That's BAD and needs to be stopped (actually i'm removing the poppler store to xml functionality in qt6 since makes no sense).

This is the first Merge Request that is a series of commits that replace the loading of the base annotation properties, later we will need to have more for AText, ALine, AGeom, etc so we can actually stop using Poppler::AnnotationUtils::storeAnnotation + Okular::AnnotationUtils::createAnnotation