Instead of having to manually stub packages that should not be
downloaded we instead automatically stub all packages (except a small
list of whitelisted ones). Tests can re-introduce the real package by
using the `realPkgs` module argument.
This update introduces support for icons.yaml in the lsd module,
enhancing the customization options for file icons.
Co-authored-by: pancho horrillo <pancho@pancho.name>
