[SizerBase] GridSplitter ResizeDirection doesn't update thumb/cursor until next interaction

### Describe the bug

Was noticing an issue where in a VSM I update the ResizeDirection of a GridSplitter between Rows to Columns (it's a splitter that can change between a horizontal doc split and a vertical one, see: XAML Studio).

However, the thumb/cursor for the Grid Splitter doesn't change from the horizontal mode to the vertical one until after the control is interacted with again.

If I also change the Orientation value, it works as expected. But since the ResizeDirection updates the Orientation value, I figured I only needed one.

### Steps to reproduce

```text
1. Create a Grid with 3 rows and 3 columns
2. Put splitter in middle
3. Swap it's ResizeDirection

(This would probably just make a good sample, I should just copy over what I have to one as another good example.)
```

### Expected behavior

Sizer updates with single changed property.

### Screenshots

_No response_

### Code Platform

- [x] UWP
- [ ] 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)
- [ ] 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

_No response_

### Visual Studio Build Number

_No response_

### Device form factor

_No response_

### Additional context

_No response_

### Help us help you

Yes, I'd like to be assigned to work on this item.

Inizia con l’implementazione di SizerBase e GridSplitter per il controllo UWP, quindi riproduci il problema modificando ResizeDirection da Rows a Columns senza interagire con lo splitter. È completato quando il thumb e il cursore si aggiornano immediatamente dopo l’unica modifica della proprietà, senza richiedere una modifica di Orientation o una seconda interazione.

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