Errors with multiple appExtensions for widgets

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### Describe the bug

Hello,
I noticed that Dev Home app has a few groups of widgets in Widgets boards. You need to install extensions to enable more widgets.

I wanted to create similar solution and put everything in one solution without creating extensions for my app, so I declared more appExtensions with different Ids and widget definition ids:

```xml

...
```

It compiles correctly without any manifest validation errors, and I can see all declared extensions as groups of widgets in the widget picker. However, there seems to be an issue. Is there a limit to the number of such extensions in the package manifest? I encounter errors when I add more than 3-5 appExtensions. Sometimes, the widgets board fails to load widgets. The second error occurs when I add a few widgets, close the board, and then reopen it. Instead of pinned widgets, I only see this message:

I modified official sample (https://github.com/microsoft/windowsappsdk-samples/tree/main/Samples/Widgets) and attached it below. You also can see my errors here: [YouTube](https://youtube.com/shorts/ySHr2P2uehU?si=oQQ2MbPjaTPcHNMv)

[cs-console-packaged.zip](https://github.com/user-attachments/files/16237748/cs-console-packaged.zip)

### Steps to reproduce the bug

1. Debug attached solution
2. Pin a few widgets from solution to the Widgets board
3. Hide and show board again

### Expected behavior

_No response_

### Screenshots

_No response_

### NuGet package version

Windows App SDK 1.5.5: 1.5.240627000

### Packaging type

Packaged (MSIX)

### Windows version

Windows 11 version 22H2 (22621, 2022 Update)

### IDE

Visual Studio 2022

### Additional context

Tested on following versions of MicrosoftWindows.Client.WebExperience:
- 524.13200.0.0
- 524.18000.0.0
- 524.19900.0.0

Start with the attached cs-console-packaged.zip and the modified Samples/Widgets solution, then reproduce the failure by pinning widgets, hiding the board, and showing it again. Compare behavior as additional manifest appExtensions are added; done means the supported extension count and the pinned-widget loading failure are reproduced and explained.

Written by the indexing model from the issue text.