(11.0 only) Roots.xml file should be removed from all templates

[maxkatz6]

Roots.xml was needed to make sure that trimming and AOT works. Now with preview5 it's not needed anymore.
Instead, to keep user applications non-trimmable, it might make sense to add TrimmableRootAssembly to the csproj instead targeting current project and same comment about compiled bindings as here https://github.com/AvaloniaUI/avalonia-dotnet-templates/blob/master/templates/csharp/app-mvvm/Roots.xml#L2.