Updating a package for multiple projects in one step results in the
NuGet package restore that is done at the end being a no-op. This
means that the project is not re-evaluated which can mean that the
AvailableItemNames are not updated. Updating a single NuGet package
does not have the same problem.

Also fixed a problem where a PackageReference project (non-sdk) was
not re-evaluated on restoring. This could also result in the
AvailableItemNames not being available to the project if the project
was missing its obj/project.assets.json file on being opened in the
IDE.