swift-package-manager

[PackageGraph] Add adaptor for using DependencyResolver on packages.

 - This provides an initial implementation of
   RepositoryPackageContainerProvider, which is an adaptor between the
   CheckoutManager part of the SCM system and the manifest schema to the
   interfaces expected by the DependencyResolver algorithm.

 - This isn't exposed via a tool yet, but does work well enough to clone real
   packages.