App Title Bar doesn't show the app icon

### Description

https://github.com/dotnet/maui/blob/13df56c765a595300d149d8a97011ef800cef73f/src/Core/src/Platform/Windows/Styles/WindowRootViewStyle.xaml#L22-L28

The AppTitleBar template references a file that doesn't exist (`Square44x44Logo.png`).

We need a way to flow the app icon file to this title bar so the icon can be displayed on the window.

### Steps to Reproduce

1. Create a new Maui project on windows
2. Try to set the app icon in the title bar of the app
3. No Icon appears in the title bar when the app is run on Windows.

### Version with bug

Release Candidate 2 (current)

### Last version that worked well

Unknown/Other

### Affected platforms

Windows

### Affected platform versions

All

### Did you find any workaround?

_No response_

### Relevant log output

_No response_

Start with src/Core/src/Platform/Windows/Styles/WindowRootViewStyle.xaml at lines 22-28 and inspect how the AppTitleBar template references Square44x44Logo.png. Trace how a new .NET MAUI Windows app provides its icon, then verify the icon appears in the title bar when running the reproduction steps on Windows.

Written by the indexing model from the issue text.