Spurious trimmer warning is not suppressed

[jkoritzinsky]

Describe the bug

@Sergio0694 and I found that the following trim warnings are emitted by a default WinUI 3 project (built with "trimmer-safe" CsWinRT projections):

1>ILLink : Trim analysis warning IL2026: WinRT.Projections..cctor(): Using member 'System.MulticastDelegate.MulticastDelegate(Object, String)' which has 'RequiresUnreferencedCodeAttribute' can break functionality when trimming application code. The target method might be removed.
1>ILLink : Trim analysis warning IL2026: WinRT.Projections..cctor(): Using member 'System.Delegate.Delegate(Object, String)' which has 'RequiresUnreferencedCodeAttribute' can break functionality when trimming application code. The target method might be removed.
1>ILLink : Trim analysis warning IL2026: WinRT.Projections..cctor(): Using member 'System.Delegate.CreateDelegate(Type, Object, String)' which has 'RequiresUnreferencedCodeAttribute' can break functionality when trimming application code. The target method might be removed.
1>ILLink : Trim analysis warning IL2026: WinRT.Projections..cctor(): Using member 'System.Delegate.CreateDelegate(Type, Object, String, Boolean, Boolean)' which has 'RequiresUnreferencedCodeAttribute' can break functionality when trimming application code. The target method might be removed.
1>ILLink : Trim analysis warning IL2026: WinRT.Projections..cctor(): Using member 'System.Delegate.CreateDelegate(Type, Object, String, Boolean)' which has 'RequiresUnreferencedCodeAttribute' can break functionality when trimming application code. The target method might be removed.

These warnings are emitted because Projections.RegisterCustomAbiTypeMappingNoLock has DynamicallyAccessedMembers(PublicMethods) on the type parameter, and a delegate type typeof(EventHandler<>) is passed in. As a result, the trimmer warns about these methods with RequiresUnreferencedCodeAttribute since it can't be sure you don't access these methods through reflection. These warnings aren't emitted by the trimmer analyzer due to dotnet/linker#3111.

These warnings should be suppressed because these methods are never invoked via reflection based on the usage.

To Reproduce

1. Create a default WinUI 3 project
2. Set <PublishTrimmed>true</PublishTrimmed>
3. Publish the project.

Expected behavior

No trimmer warnings from WinRT.Runtime.dll

Version Info

VS2022.4

Additional context

@Sergio0694 has a repro.