Reinstate ProjectLoadCheckpoint for NuGetRestoreService

[drewnoakes]

#9728 introduced metadata to instances of IProjectDynamicLoadComponent resembling:

[ProjectDynamicLoadComponent(ProjectLoadCheckpoint.AfterLoadInitialConfiguration)]

This metadata controls when the component is initialized during project construction.

On the NuGetRestoreService, this metadata broke package restore for C++/CLI projects.

We are commenting out the metadata for now. This issue is tracking the desire to add it back again in future in a way that doesn't cause problems for C++/CLI projects.

[drewnoakes]

Moyo found that this must also be commented out on PackageRestoreDataSource.

Internal bug: https://devdiv.visualstudio.com/DevDiv/_workitems/edit/2567065