Implement SolutionPackager task

[TomProkop]

Implement solution packaging directly through .NET assemblies instead od spawning a PAC CLI process. Use bolt.module.solution for support of Canvas app packing. Internally it calls SolutionPackagerLib.dll.

Assemblies are shipped with Microsoft.PowerApps.CLI NuGet package.

• Include and load Microsoft first-party assemblies from PAC CLI
• Implement InvokeSolutionPackager custom task
• Validate that the required assemblies are copied over to the NuGet package (update the .nuspec file)
• Test with a real project and create unit tests for the custom task