Context menu cleanup (#40584)

Addressing items in #40583

- [x] When navigating the context menu with the up/down keys, separators
should not be selectable.
- [x] [For context items with a super long title, we need to trim those
with an ellipsis. Ideally, we'd show a tooltip for just those
items.](https://github.com/microsoft/PowerToys/issues/40313)
- [x] [Context menu search bar text size doesn't update after changing
system text size](https://github.com/microsoft/PowerToys/issues/39648)
- [x] Weird "kick out" on first context menu item
- [x] [Primary button doesn't work if the command has more items (fix
regression)](https://github.com/microsoft/PowerToys/issues/40624)

Example of long context menu item titles with tooltips: (@niels9001,
look okay?)


https://github.com/user-attachments/assets/fc0a4034-9c22-48ee-a3f0-44fcc2f294a6

closes #40624

src/modules/cmdpal/Microsoft.CmdPal.UI/Controls/CommandBar.xaml.cs

@@ -6,13 +6,11 @@ using CommunityToolkit.Mvvm.Messaging;
 using Microsoft.CmdPal.Core.ViewModels;
 using Microsoft.CmdPal.Core.ViewModels.Messages;
 using Microsoft.CmdPal.UI.Views;
-using Microsoft.UI.Input;
 using Microsoft.UI.Xaml;
 using Microsoft.UI.Xaml.Controls;
 using Microsoft.UI.Xaml.Controls.Primitives;
 using Microsoft.UI.Xaml.Input;
 using Windows.System;
-using Windows.UI.Core;
 
 namespace Microsoft.CmdPal.UI.Controls;