[Swift shipping] Implement testing framework

[kotlarmilos]

Infrastructure

• [SwiftBindings] Setup xunit testing framework #2871
• [Swift bindings] Make projection tooling AOT compatible #2880
• [Swift shipping] Setup MacCatalyst tests on the CI #2998
• [Swift shipping] Create Swift.Bindings.Experimental and tooling NuGet packages in the dotnet-experimental feed #2849
• [Projection tooling] Surface build errors #3006