Integration testing of the dotnet new templates

[ghuntley]

What would you like to be added:

Integration tests could look like as follows:

1. A folder containing different generated uno apps/projects (test cases) either generated on the spot or statically stored in git.
2. Building each one of these apps.
3. Asserting no build failures.

Why is this needed:

There's an entire class of issues which we don't have a safety harness
Prevent regressions of (add items here so we can track test scenarios):

• Projects with with ".Uno" in their name aka "MyCoolApp.Uno*
• Projects with spaces in their name aka "My Cool App"
• App.xaml without resources NRE

For which Platform:

• iOS
• Android
• WebAssembly
• WebAssembly renderers for Xamarin.Forms
• Windows
• Build tasks
• Solution Templates

Anything else we need to know?

Potential dependency on migration to the .NET core template system instead of vsix.