TargetInvocationException when using a DependencyProperty bound to ObservableCollection<Guid?>

### Describe the bug

The attached project illustrates our problem. We have an ObservableCollection that we bind to a DependencyProperty and use to display a list and a counter of unique IDs. Up until Visual Studio v 17.11.4 this was working fine, but after upgrading to 17.11.5 (and the WindowsAppSDK from 1.5.240428000 to 1.6.240923002) the following exception pasted below started happening during startup and the initial setting of the property. We worked around this temporarily by staying at VS 17.11.4 and the older WindowsAppSDK, but this week it seems like devops pipelines has upgraded to the new version, causing all our builds to crash with the same error during startup. This also confirms that the issue happens if you run VS 17.11.5 (assuming that's what the devops runner is using), and WindowsAppSDK 1.5.240428000.

```
System.Reflection.TargetInvocationException
HResult=0x80131604
Message=Exception has been thrown by the target of an invocation.
Source=System.Private.CoreLib
StackTrace:
at System.RuntimeFieldHandle.GetValue(RtFieldInfo field, Object instance, RuntimeType fieldType, RuntimeType declaringType, Boolean& domainInitialized)
at System.Reflection.RtFieldInfo.GetValue(Object obj)
at WinRT.GuidGenerator.GetIID(Type type)
at WinRT.ComWrappersSupport.g__AddInterfaceToVtable|16_1(Type iface, List`1 entries, Boolean hasCustomIMarshalInterface)
at WinRT.ComWrappersSupport.g__GetInterfaceTableEntriesForJitEnvironment|16_2(Type type, List`1 entries, Boolean hasCustomIMarshalInterface)
at WinRT.ComWrappersSupport.GetInterfaceTableEntries(Type type)
at WinRT.DefaultComWrappers.<>c.b__7_0(Type type)
at System.Runtime.CompilerServices.ConditionalWeakTable`2.GetValueLocked(TKey key, CreateValueCallback createValueCallback)
at System.Runtime.CompilerServices.ConditionalWeakTable`2.GetValue(TKey key, CreateValueCallback createValueCallback)
at WinRT.DefaultComWrappers.ComputeVtables(Object obj, CreateComInterfaceFlags flags, Int32& count)
at System.Runtime.InteropServices.ComWrappers.TryGetOrCreateComInterfaceForObjectInternal(ObjectHandleOnStack comWrappersImpl, Int64 wrapperId, ObjectHandleOnStack instance, CreateComInterfaceFlags flags, IntPtr& retValue)
at System.Runtime.InteropServices.ComWrappers.TryGetOrCreateComInterfaceForObjectInternal(ComWrappers impl, Object instance, CreateComInterfaceFlags flags, IntPtr& retValue)
at System.Runtime.InteropServices.ComWrappers.GetOrCreateComInterfaceForObject(Object instance, CreateComInterfaceFlags flags)
at WinRT.ComWrappersSupport.CreateCCWForObjectForABI(Object obj, Guid iid)
at WinRT.ComWrappersSupport.CreateCCWForObjectForMarshaling(Object obj, Guid iid)
at WinRT.MarshalInspectable`1.CreateMarshaler2(T o, Guid iid, Boolean unwrapObject)
at WinRT.MarshalInspectable`1.CreateMarshaler2(T o, Boolean unwrapObject)
at ABI.Microsoft.UI.Xaml.IDependencyObjectMethods.SetValue(IObjectReference _obj, DependencyProperty dp, Object value)
at Microsoft.UI.Xaml.DependencyObject.SetValue(DependencyProperty dp, Object value)
at TestNullableGuidObservableCollection.SelectionCounter.set_SelectedItems(ObservableCollection`1 value) in C:\Users\martin\source\repos\TestNullableGuidObservableCollection\TestNullableGuidObservableCollection\SelectionCounter.xaml.cs:line 43
at TestNullableGuidObservableCollection.MainWindow.XamlBindingSetters.Set_TestNullableGuidObservableCollection_SelectionCounter_SelectedItems(SelectionCounter obj, ObservableCollection`1 value, String targetNullValue) in C:\Users\martin\source\repos\TestNullableGuidObservableCollection\TestNullableGuidObservableCollection\obj\x64\Debug\net8.0-windows10.0.19041.0\MainWindow.g.cs:line 27
at TestNullableGuidObservableCollection.MainWindow.MainWindow_obj1_Bindings.Update_SelectedItems(ObservableCollection`1 obj, Int32 phase) in C:\Users\martin\source\repos\TestNullableGuidObservableCollection\TestNullableGuidObservableCollection\obj\x64\Debug\net8.0-windows10.0.19041.0\MainWindow.g.cs:line 178
at TestNullableGuidObservableCollection.MainWindow.MainWindow_obj1_Bindings.Update_(MainWindow obj, Int32 phase) in C:\Users\martin\source\repos\TestNullableGuidObservableCollection\TestNullableGuidObservableCollection\obj\x64\Debug\net8.0-windows10.0.19041.0\MainWindow.g.cs:line 165
at TestNullableGuidObservableCollection.MainWindow.MainWindow_obj1_Bindings.Update() in C:\Users\martin\source\repos\TestNullableGuidObservableCollection\TestNullableGuidObservableCollection\obj\x64\Debug\net8.0-windows10.0.19041.0\MainWindow.g.cs:line 122
at TestNullableGuidObservableCollection.MainWindow.MainWindow_obj1_Bindings.Initialize() in C:\Users\martin\source\repos\TestNullableGuidObservableCollection\TestNullableGuidObservableCollection\obj\x64\Debug\net8.0-windows10.0.19041.0\MainWindow.g.cs:line 116
at TestNullableGuidObservableCollection.MainWindow.MainWindow_obj1_Bindings.Activated(Object obj, WindowActivatedEventArgs data) in C:\Users\martin\source\repos\TestNullableGuidObservableCollection\TestNullableGuidObservableCollection\obj\x64\Debug\net8.0-windows10.0.19041.0\MainWindow.g.cs:line 150
at WinRT._EventSource_global__Windows_Foundation_TypedEventHandler_object__global__Microsoft_UI_Xaml_WindowActivatedEventArgs_.EventState.b__1_0(Object sender, WindowActivatedEventArgs args)
at WinRT.GenericTypeInstantiations.Windows_Foundation_TypedEventHandler_2_object__Microsoft_UI_Xaml_WindowActivatedEventArgs.Do_Abi_Invoke(IntPtr thisPtr, IntPtr sender, IntPtr args)

This exception was originally thrown at this call stack:
[External Code]

Inner Exception 1:
TypeInitializationException: The type initializer for 'ABI.System.Collections.Generic.IList`1' threw an exception.

Inner Exception 2:
TypeInitializationException: The type initializer for 'ABI.System.Collections.Generic.IListMethods`1' threw an exception.

Inner Exception 3:
ArgumentException: GenericArguments[1], 'ABI.System.Nullable`1[System.Guid]', on 'ABI.System.Collections.Generic.IListMethods`2[T,TAbi]' violates the constraint of type 'TAbi'.

Inner Exception 4:
TypeLoadException: GenericArguments[1], 'ABI.System.Nullable`1[System.Guid]', on 'ABI.System.Collections.Generic.IListMethods`2[T,TAbi]' violates the constraint of type parameter 'TAbi'.
```
[TestNullableGuidObservableCollection.zip](https://github.com/user-attachments/files/17494577/TestNullableGuidObservableCollection.zip)

### Steps to reproduce the bug

1. Open the attached example solution
2. Build and run
3. The exception above happens during startup

### Expected behavior

For the attached application to start up fine, and no error to occur.

### Screenshots

_No response_

### NuGet package version

WinUI 3 - Windows App SDK 1.6.1: 1.6.240923002

### Windows version

Windows 11 (21H2): Build 22000

### Additional context

_No response_

Start with the attached TestNullableGuidObservableCollection project and reproduce the startup failure using Windows App SDK 1.6.1. Inspect SelectionCounter.xaml.cs line 43 and the WinRT.GuidGenerator/IListMethods stack trace to identify the nullable Guid marshaling failure. Done means the sample starts without the TargetInvocationException while retaining the ObservableCollection binding.

Written by the indexing model from the issue text.