* Trivial: Take a nested function out of a foreach loop

* Deprecate PackageManager.loadSCMPackage's Dependency overload, use Repository

We're moving away from using `Dependency.m_range` to store the git ref,
and the `Repository` type has already been updated to include the information,
but some places still read it from `m_range`, including this one.

* Trivial: Forward Dependency's string ctor to VersionRange ctor

* Trivial: Simplify comparison with `VersionRange.Invalid` within `VersionRange`