CmdPal: Handle an empty icon in dock items (#45968)

## Summary of the Pull Request

This PR allows dock to handle items without an icon better:

- Hides the icon element when a dock item is not visible and center text
labels in vertical dock modes.
- Adds an icon to clock dock wrapper, so it appears in settings.
- Stretches buttons with icon and labels in the vertical docks to the
full width.
- Fixes `IconInfoViewModel.IconForTheme` method implementation.

## Pictures? Pictures!

Horizontal Dock:

<img width="393" height="84" alt="image"
src="https://github.com/user-attachments/assets/d12aa406-da9d-4bd2-b464-595deab41d2e"
/>

<img width="390" height="105" alt="image"
src="https://github.com/user-attachments/assets/c28d65c0-1023-47d0-9ff5-85c74a18c342"
/>


Vertical Dock:

<img width="153" height="258" alt="image"
src="https://github.com/user-attachments/assets/e1be59d9-fa1f-4a24-b0c1-e8cff4211906"
/>

Settings:

<img width="1266" height="713" alt="image"
src="https://github.com/user-attachments/assets/722d47da-c668-4df2-9f1d-bf7808333be4"
/>



<!-- Please review the items on the PR checklist before submitting-->
## PR Checklist

- [x] Closes: #45955

src/modules/cmdpal/Microsoft.CmdPal.UI.ViewModels/IconInfoViewModel.cs

@@ -22,7 +22,7 @@ public partial class IconInfoViewModel : ObservableObject, IIconInfo
 
     public IconDataViewModel Dark { get; private set; }
 
-    public IconDataViewModel IconForTheme(bool light) => Light = light ? Light : Dark;
+    public IconDataViewModel IconForTheme(bool light) => light ? Light : Dark;
 
     public bool HasIcon(bool light) => IconForTheme(light).HasIcon;