Layout issue with WrapLayout inside ItemsRepeater.

### Describe the bug

When I update the contents of the ItemsRepeater with the container off screen, the items bunch up. This only happens when the container is update off screen and fixes as soon as the next UI update happens.

### Steps to reproduce

```text
1. Use WrapLayout inside ItemsRepeater.

2. You have to be able to scroll away from the container and add an element to it.
3. After adding to it, scroll back up, observe bunching.
```

### Expected behavior

Items should have the correct layout.

### Screenshots

### Code Platform

- [ ] UWP
- [x] WinAppSDK / WinUI 3
- [ ] Web Assembly (WASM)
- [ ] Android
- [ ] iOS
- [ ] MacOS
- [ ] Linux / GTK

### Windows Build Number

- [ ] Windows 10 1809 (Build 17763)
- [ ] Windows 10 1903 (Build 18362)
- [ ] Windows 10 1909 (Build 18363)
- [ ] Windows 10 2004 (Build 19041)
- [ ] Windows 10 20H2 (Build 19042)
- [ ] Windows 10 21H1 (Build 19043)
- [ ] Windows 10 21H2 (Build 19044)
- [x] Windows 10 22H2 (Build 19045)
- [ ] Windows 11 21H2 (Build 22000)
- [ ] Other (specify)

### Other Windows Build number

_No response_

### App minimum and target SDK version

- [ ] Windows 10, version 1809 (Build 17763)
- [ ] Windows 10, version 1903 (Build 18362)
- [ ] Windows 10, version 1909 (Build 18363)
- [ ] Windows 10, version 2004 (Build 19041)
- [ ] Windows 10, version 2104 (Build 20348)
- [ ] Windows 11, version 22H2 (Build 22000)
- [ ] Other (specify)

### Other SDK version

_No response_

### Visual Studio Version

2022

### Visual Studio Build Number

Microsoft Visual Studio Community 2022 (ARM 64-bit) - Current / Version 17.14.3

### Device form factor

Desktop

### Additional context

_No response_

### Help us help you

No, I'm unable to contribute a solution.

Start by reproducing the issue with WrapLayout inside an ItemsRepeater in a WinAppSDK/WinUI 3 desktop app. Update the repeater while its container is off screen, scroll back, and inspect the layout behavior; done means items retain the correct spacing and arrangement without requiring another UI update.

Scritto dal modello di indicizzazione a partire dal testo della issue.