GitHub Actions: macOS virtual environment updated to Catalina
The GitHub Actions macOS virtual environment has been upgraded to Catalina (v10.15). Jobs using the `macos-10.14` virtual environment will not run and must be migrated to use `macos-latest`. In addition to Catalina, other changes include: Xcode 11.1 will be set as default Mono 6.4, Xamarin.iOS 13.4, Xamarin.Android 10.0, Xamarin.Mac 6.2 will be set as default .NET Core 3.0 will be set as default…