Create nuget package diff tooling

[mmitche]

Create a tool and msbuild task to find any differences between nuget packages produced by the VMR and the official build.

• [x] File structure
• [ ] Nuspec properties
• [x] Assembly versions
• [x] Handle expected differences
• [x] #4106

[dotnet-issue-labeler[bot]]

I couldn't figure out the best area label to add to this issue. If you have write-permissions please help me learn by adding exactly one area label.

[tkapin]

Is this a duplicate of #3819?

[mmitche]

Subitem in the epic.

[mmitche]

@jtschuster update as necessary