CmdPal: Replace Tapped events with generic ones (#40640)

## Summary of the Pull Request
Click event on WinUI buttons handle more than just click and is more
versatile that Tapped event. When you tap a Button with a finger or
stylus, or press a left mouse button while the pointer is over it, the
button raises the Click event. If a button has keyboard focus, pressing
the Enter key or the Spacebar key also raises the Click event.

This PR also replaces the right-tapped event on items on the list page
with context menu handling, allowing other input gestures (such as
Shift+F10) to also display the context menu.

And finally, it adds a button to the status messages badge so that the
flyout can be opened using the keyboard.

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

- [x] **Closes:** #40616 
- [ ] **Communication:** I've discussed this with core contributors
already. If the work hasn't been agreed, this work might be rejected
- [ ] **Tests:** Added/updated and all pass
- [ ] **Localization:** All end-user-facing strings can be localized
- [ ] **Dev docs:** Added/updated
- [ ] **New binaries:** Added on the required places
- [ ] [JSON for
signing](https://github.com/microsoft/PowerToys/blob/main/.pipelines/ESRPSigning_core.json)
for new binaries
- [ ] [WXS for
installer](https://github.com/microsoft/PowerToys/blob/main/installer/PowerToysSetup/Product.wxs)
for new binaries and localization folder
- [ ] [YML for CI
pipeline](https://github.com/microsoft/PowerToys/blob/main/.pipelines/ci/templates/build-powertoys-steps.yml)
for new test projects
- [ ] [YML for signed
pipeline](https://github.com/microsoft/PowerToys/blob/main/.pipelines/release.yml)
- [ ] **Documentation updated:** If checked, please file a pull request
on [our docs
repo](https://github.com/MicrosoftDocs/windows-uwp/tree/docs/hub/powertoys)
and link it here: #xxx

<!-- Provide a more detailed description of the PR, other things fixed,
or any additional comments/features here -->
## Detailed Description of the Pull Request / Additional comments

<!-- Describe how you validated the behavior. Add automated tests
wherever possible, but list manual validation steps taken as well -->
## Validation Steps Performed

Tested on desktop with keyboard and mouse (no cats), and SB2 with touch
and pen. Input gestures seem to work as intended.

---------

Co-authored-by: Mike Griese <migrie@microsoft.com>

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

@@ -413,7 +413,7 @@ public sealed partial class ShellPage : Microsoft.UI.Xaml.Controls.Page,
         }
     }
 
-    private void BackButton_Tapped(object sender, Microsoft.UI.Xaml.Input.TappedRoutedEventArgs e) => WeakReferenceMessenger.Default.Send<NavigateBackMessage>(new());
+    private void BackButton_Clicked(object sender, Microsoft.UI.Xaml.RoutedEventArgs e) => WeakReferenceMessenger.Default.Send<NavigateBackMessage>(new());
 
     private void RootFrame_Navigated(object sender, Microsoft.UI.Xaml.Navigation.NavigationEventArgs e)
     {