Support compiled bindings for generic ViewModels

[StepKie]

Please support compiled bindings for ViewModels based on a generic type.

Sample:

• classes: MyViewModel<T>, MyModel
• in code-behind: BindingContext = new MyViewModel<MyModel>()

In Xaml, I want to bind

x:DataType="viewmodels:MyViewModel(models:MyModel)"

Originally posted by @StephaneDelcroix in #20568 (comment)

@StephaneDelcroix, according to your offer, should I create an issue for this now, and tag-mention you? Just want to make sure before doing so that this is a real issue and I am not doing something obvious wrong with x:DataType="viewmodels:BoViewModel(models:BoArticle)"

@Hottemax please do

There was a similar request in the Xamarin.Forms github: xamarin/Xamarin.Forms#7161

[StephaneDelcroix]

we would need to support this syntax for x:Type as well.

currently, we're using the type as a string, but we should use the TypeArgumentsParser we already use elsewhere