Binary compatibility cleanup list

[kekekeks]

Since we are keeping binary compatibility with the latest nuget release, some design choices are sub-optimal in the long term.
This issue serves as a tracker for breaking changes that should be done during the preparation phase of the next version.

• - Added support for non-control templates in XAML #6665 - ControlTemplateResult should be completely replaced with TemplareResult<IControl>
• - Core libraries merge, see Merge core libraries. #5831
• - AppBuilder (see Move AppBuilder to netstandard2.0 library #7052)
• - WindowRoot (Window shouldn't be a TopLevel #7063)
• - Remove various things that have been [Obsolete] for ages, e.g. DropDown
• - Separate class and struct overloads for property registration (Nullable annotations for AvaloniaObject/AvaloniaProperty etc. #7078 (comment))
• - Add [Unstable] (or something) attributes to platform types to hide them from ApiCompat and properly document our stable API
• - Standardize Pointer Event Names with WinUI
• - Make PointerPoint to be a struct rather than a class
• - Remove public constructors for KeyEventArgs, PointerEventArgs and friends.
• - Remove generic virtual methods from the public API
• - Refactor transparency hints
• Remove many unneeded interfaces (IVisual, ILayoutable, IControl etc) and use concrete classes (Breaking Change: Remove Unneeded Interfaces #9495)

[grokys]

Currently AvaloniaLocator.GetService can return null if a service isn't found. This results in a lot of potential NREs. Should we change it to throw if the service is not found and add a TryGetService method?

[jp2masa]

For reference, Microsoft.Extensions.DependencyInjection has GetService and GetRequiredService for this purpose I believe: https://docs.microsoft.com/en-us/dotnet/api/microsoft.extensions.dependencyinjection.serviceproviderserviceextensions?view=dotnet-plat-ext-6.0#methods.

(I'm personally not a fan of this pattern, but if you want to be consistent with official Microsoft packages I think this is relevant.)

[danwalmsley]

Remove ClientSize, Width / Height should be sufficient and we have FrameSize also.

[danwalmsley]

Might as well put this here:
Provide windows ARM64 binaries for libgles etc. (all that is needed for just works arm on windows support)