XAML generated code can result in an InvalidCastException inside the IComponentConnector Connect method

### Describe the bug

I updated to 1.7.250606001, tried to run my app as normal, and received an InvalidCastException for WinRT.IInspectable to Microsoft.UI.Xaml.Controls.FontIcon.

I reverted to 1.7.250513003, and the error is gone.

### Steps to reproduce the bug

It's a large app, I set FontIcons in XAML in many places.

Something in 1.7.250606001 changed how these are handled.

### Expected behavior

_No response_

### Screenshots

_No response_

### NuGet package version

WinUI 3 - Windows App SDK 1.7.3: 1.7.250606001

### Windows version

Windows 10 (21H2): Build 19044

### Additional context

_No response_

Start at the generated XAML code's IComponentConnector.Connect method and compare its handling of FontIcon between Windows App SDK 1.7.250606001 and 1.7.250513003. Reproduce the InvalidCastException in a focused app with FontIcon declarations, then confirm the newer version no longer casts WinRT.IInspectable to Microsoft.UI.Xaml.Controls.FontIcon incorrectly.

Written by the indexing model from the issue text.