TreeViewItem does not handle IsExpanded binding correctly

### Describe the bug

After clicking the Collapse button (which sets the IsExpanded property of all bound data items to False), then clicking the Expand button (which sets the IsExpanded property of all bound data items to True), not all TreeViewItem elements fully expand.

### Steps to reproduce the bug

1. Clone https://github.com/GochenRyan/WinUI3TreeViewBug
2. Checkout commit 7272036ec4013931b2a483e537b8f1bf2d952227
3. Set ExpandBug as startup project
4. Build and run

### Expected behavior

All TreeViewItem elements fully expand.

### Screenshots


### NuGet package version

WinUI 3 - Windows App SDK 1.6.1: 1.6.240923002

### Windows version

Windows Insider Build (xxxxx)

### Additional context

_No response_

Clone the linked WinUI3TreeViewBug repository, check out commit 7272036ec4013931b2a483e537b8f1bf2d952227, and set ExpandBug as the startup project. Build and run it, then reproduce the Collapse and Expand sequence described in the issue. Done means every TreeViewItem fully expands after the bound items are set back to True.

Written by the indexing model from the issue text.