Add a DynamicallyAccessedMembers attribute to ViewBuilder.Create

[Numpsy]

(sort of) refs #281.

So... I've been using FuncUI to build an app that i've been publishing as a self contained, trimmed, exe (it's built with .NET 7, but you can run it without having to have an appropriate .NET version installed, and has fewer files to care about).

For various reasons (many things being broken basically), I've had it on partial trim mode so that it only trims libs that are explicitly marked as trimmable, whilst waiting for thins to get fixed or improve elsewhere. (e.g. the completion of some work in Avalonia to help it work better with trimming).

In Avalonia 11 Preview 6, parts of Avalonia are marked as trimmable, so they will be trimmed now when they weren't before. This should be quite nice as it will remove controls you aren't using and such, but alas it also causes this to happen with FuncUI:

Exception Info: System.MissingMethodException: Cannot dynamically create an instance of type 'Avalonia.Controls.TreeView'. Reason: No parameterless constructor defined.
   at System.RuntimeType.ActivatorCache..ctor(RuntimeType)
   at System.RuntimeType.CreateInstanceDefaultCtor(Boolean, Boolean)
   at System.Activator.CreateInstance(Type, Boolean, Boolean)
   at System.Activator.CreateInstance(Type , Boolean)
   at System.Activator.CreateInstance(Type )
   at Avalonia.FuncUI.VirtualDom.Patcher.create(ViewDelta viewElement)
   at Avalonia.FuncUI.VirtualDom.VirtualDom.updateBorderRoot(Border host, FSharpOption`1 last, FSharpOption`1 next)
   at <StartupCode$Avalonia-FuncUI>.$Component.Update@24.Invoke()
   at Avalonia.Threading.JobRunner.Job.Avalonia.Threading.JobRunner.IJob.Run() in /_/src/Avalonia.Base/Threading/JobRunner.cs:line 193
   at Avalonia.Threading.JobRunner.RunJobs(Nullable`1) in /_/src/Avalonia.Base/Threading/JobRunner.cs:line 38
   at Avalonia.Win32.Win32Platform.WndProc(IntPtr, UInt32, IntPtr, IntPtr) in /_/src/Windows/Avalonia.Win32/Win32Platform.cs:line 267
   at Avalonia.Win32.Interop.UnmanagedMethods.DispatchMessage(MSG&)
   at Avalonia.Win32.Win32Platform.RunLoop(CancellationToken) in /_/src/Windows/Avalonia.Win32/Win32Platform.cs:line 215
   at Avalonia.Threading.Dispatcher.MainLoop(CancellationToken) in /_/src/Avalonia.Base/Threading/Dispatcher.cs:line 61
   at Avalonia.Controls.ApplicationLifetimes.ClassicDesktopStyleApplicationLifetime.Start(String[]) in /_/src/Avalonia.Controls/ApplicationLifetimes/ClassicDesktopStyleApplicationLifetime.cs:line 122
   at Avalonia.ClassicDesktopStyleApplicationLifetimeExtensions.StartWithClassicDesktopLifetime(AppBuilder, String[], ShutdownMode ) in /_/src/Avalonia.Controls/ApplicationLifetimes/ClassicDesktopStyleApplicationLifetime.cs:line 214

because the trimmer can't find any references to said constructor and therefore bins it.
Activator.CreateInstance is annotated to explain this and in C# there is a roslyn analyzer that will try to tell you about that so that you can annotate your own code to be compatible, but no such help in F#.

Anyway, I'm sure there are other code paths that have the same issue (e.g. the ones that create instances of things and use a constructor with parameters), but just doing this one fixes the issues i'm getting by making it retain all the default constructors for used controls, so I'm opening this to at least open the question on how this situation should be handled.

[JaggerJo]

Yeah, excellent point. I can think of a few ways of fixing constructors with parameters. We can merge this already.

[Numpsy]

I hadn't tried it before, but fwiw this change also allows a self-contained/trimmed version of the control catalog to run, whereas without that it just crashed on startup because of missing constructors

Edit: With .Net 6 that is - with 7 full trimming still breaks itfor other reasons