[XC] Produce warning when x:DataType is inherited from outer scope of DataTemplate

[simonrozsival]

Description of Change

Produces the following warning:

path/to/document.xaml(1, 2): XamlC warning XC0024: Binding might be compiled incorrectly since the x:DataType annotation comes from an outer scope. Make sure you annotate all DataTemplate XAML elements with the correct x:DataType. See https://learn.microsoft.com/dotnet/maui/fundamentals/data-binding/compiled-bindings for more information.

• Please feel free to suggest changes to the warning message.
• The docs will need to be updated to reflect this change if this gets merged

Issues Fixed

Fixes #22714

/cc @StephaneDelcroix @jonathanpeppers @PureWeen @mattleibow

[jonathanpeppers]

Are there any other types of scopes we would need future changes for?

Wondering if any of these have an issue:

• ResourceDictionary
• ControlTemplate

In theory, you could have a {Binding} inside a Style in a {ResourceDictionary} and the type could be different based on the XAML using the Style? Maybe the existing warning already works for this case.

[simonrozsival]

I don't think this applies to ResourceDictionary (BTW we're not compiling these bindings at the moment: #22023), but it might apply to ControlTemplate 🤔 In general, this should be whenever there's a different BindingContext in the outer scope and in the inner scope. What do you think, @StephaneDelcroix?

[jonathanpeppers]

I think the other cases we can check in the future.

[rmarinho]

Sorry needs rebase

[simonrozsival]

@rmarinho @jonathanpeppers do you think we can go ahead with this PR? There are currently no merge conflicts.