CmdPal: Refactoring ContextMenu adding separators, IsCritical styling, and right-click context menus for list items (#40189)

Refactored ContextMenu into it's own control to allow displaying in
CommandBar and in response to right click on list items.

- Adds "critical" styling to context menu items flagged as `IsCritical`.
This will use the theme to style with correct color.
- Added `SeparatorContextItem` and modified `MoreCommands` to allow for
both `CommandContextItem`s and `SeparatorContextItem`s.
- Right clicking a list item with a context menu will open the context
menu at the position of the click and position the filter box at the top
of the context menu.


![image](https://github.com/user-attachments/assets/3bef6b04-28bb-4a17-b731-d9ed20c0566f)


![image](https://github.com/user-attachments/assets/37ed497c-6d98-4f04-8114-d9952127ca2e)


This PR covers:

- closes #38308
- closes #39211
- closes #38307
- closes #38261

src/modules/cmdpal/Microsoft.CmdPal.UI/Pages/ShellPage.xaml.cs

@@ -17,6 +17,7 @@ using Microsoft.Extensions.DependencyInjection;
 using Microsoft.PowerToys.Telemetry;
 using Microsoft.UI.Dispatching;
 using Microsoft.UI.Xaml.Controls;
+using Microsoft.UI.Xaml.Controls.Primitives;
 using Microsoft.UI.Xaml.Media.Animation;
 using DispatcherQueue = Microsoft.UI.Dispatching.DispatcherQueue;