Port uses of Newtonsoft.Json to System.Text.Json where possible

[ahsonkhan]

The following templating libraries pull in Newtonsoft.Json:

• - Microsoft.TemplateEngine.Edge
• - Microsoft.TemplateEngine.Orchestrator.RunnableProjects
• - Microsoft.TemplateEngine.Cli

We need to investigate if these assemblies can be updated to remove their dependency on Newtonsoft.Json.

Links for Context:

• The future of JSON in .NET Core 3.0 announcements#90
• https://github.com/dotnet/corefx/issues/33115

Source and docs:

• https://github.com/dotnet/corefx/tree/master/src/System.Text.Json/roadmap
• https://github.com/dotnet/corefx/tree/master/src/System.Text.Json/source_package
• https://github.com/dotnet/corefx/tree/master/src/System.Text.Json/porting_guide

The library is available as a source package and in-box assembly in .NET Core 3.0:

• https://blogs.msdn.microsoft.com/dotnet/2019/01/29/announcing-net-core-3-preview-2/
• https://aka.ms/netcore3download
• https://www.nuget.org/packages/Microsoft.Bcl.Json.Sources/4.6.0-preview.19073.11

Newly added serialization API:
https://github.com/dotnet/corefx/blob/0ad52826f3cfad89a90eb2c21ccfc131bd36646b/src/System.Text.Json/ref/System.Text.Json.cs#L300-L326

Upcoming APIs:
https://github.com/dotnet/corefx/issues/34372
https://github.com/dotnet/corefx/issues/34894

cc @mlorbetske, @seancpeters, @vijayrkn, @joshfree, @bartonjs, @steveharter

[mlorbetske]

@ahsonkhan could you post a link to the documentation (or source location) for the new APIs?

[ahsonkhan]

could you post a link to the documentation (or source location) for the new APIs?

Done. I knew I was forgetting something :)

[mlorbetske]

@ahsonkhan thanks!