All packages installed by pmbootstrap have dependencies that can't get automatically removed

Created by: ollieparanoid

@drebrez wrote in https://github.com/postmarketOS/pmbootstrap/issues/1188#issuecomment-363605460:

I've tried adding the fbdebug package to the dependencies of the postmarketos-mkinitfs-hook-debug-shell, but when I run pmbootstrap initfs hook_del debug-shell it doesn't uninstall the fbdebug package from the chroot.

The thing is, pmbootstrap resolves all dependencies on its own, and then explicitly lists all packages that should be installed in the apk add command. That means, when one wants to uninstall a certain package, all dependencies that have been installed by pmbootstrap are still marked as explicitly installed and do not get automatically removed.