[DotNetPlanner] add installing packages to InstallStage

[savil]

Summary

In .Net, the package manager is called NuGet. https://www.nuget.org

dotnet restore is the equivalent of pip install. I add this to the InstallStage.

And ensure we do not do restore during dotnet publish and dotnet run (which it implicitly does otherwise)

How was it tested?

addded testcase that adds a package for json: https://www.nuget.org/packages/Newtonsoft.Json/

> devbox build
> docker run devbox
serialized json for csharp_10_dotnet_6_with_package.Product is {"Name":"Apple","Expiry":"2008-12-28T00:00:00","Sizes":["Small"]}

[savil]

Current dependencies on/for this PR:

• main
  • PR [DotNetPlanner] add installing packages to InstallStage #142 👈

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[gcurtis]

My C# is a bit rusty, but from what I can remember everything looks good to me!