Change wallpaper activity to StandalonePreviewActivity

Description

Use StandalonePreviewActivity for cropping and setting the wallpaper, which applies the offsets correctly on home screen.

Screenshots

wallpaper-activity

Issues

https://gitlab.e.foundation/e/os/backlog/-/issues/519

10 commandments of code reviews

👪 ❤️ https://gitlab.e.foundation/internal/wiki/-/wikis/development/code-review