HaikuDepot: Add PackageInfo flag for system dependencies.
HaikuDepot: Disallow actions on system deps as well.
HaikuDepot: Resolve system dependencies.

- While building the installed package list, resolve the dependencies
  of the OS packages. Flag the resulting list as protected so as
  to disallow uninstallation of them in addition to the OS packages.
HaikuDepot: Add TODO note.