[UX] New dashboard & refactored KeyVisual (#40214)

### Updated `KeyVisual` and `Shortcut` control
- Refactoring `KeyVisual` to remove redundant properties and UI
elements, and using Styles for better customization.
- Shortcut control now shows a "Configure shortcut" label when there's
no shortcut configured.

### Other changes
- Consolidated converters that were used across pages in `App.xaml.cs`
with consistent naming.
- Renamed templated controls (from `.cs` to `.xaml.cs`) and moving those
to the `Controls` root folder vs. individual folders for a better
overview.
<!-- Please review the items on the PR checklist before submitting-->
## PR Checklist

Closes #39520
Closes #32944

---------

Co-authored-by: Jay <65828559+Jay-o-Way@users.noreply.github.com>
Co-authored-by: Jaylyn Barbee <51131738+Jaylyn-Barbee@users.noreply.github.com>

src/settings-ui/Settings.UI.Library/HotkeySettings.cs

@@ -120,9 +120,7 @@ namespace Microsoft.PowerToys.Settings.UI.Library
 
             if (Shift)
             {
-                shortcutList.Add("Shift");
-
-                // shortcutList.Add(16); // The Shift key or button.
+                shortcutList.Add(16); // The Shift key or button.
             }
 
             if (Code > 0)