Add lowpkg.unpurge for dpkg
apt: add purge_desired argument to pkg.list_pkgs
"unpurge" packages marked for purge in pkg.installed states

See https://github.com/saltstack/salt/issues/10719.
Make other pkg providers properly handle purge_desired
Merge pull request #10989 from terminalmage/10719

"unpurge" pkgs marked for purge in pkg.installed states