[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/SettingsXAML/Controls/FlyoutMenuButton.xaml.cs

@@ -0,0 +1,40 @@
+// Copyright (c) Microsoft Corporation
+// The Microsoft Corporation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using Microsoft.UI.Xaml;
+using Microsoft.UI.Xaml.Controls;
+
+namespace Microsoft.PowerToys.Settings.UI.Controls
+{
+    public partial class FlyoutMenuButton : Button
+    {
+        /// <summary>
+        /// The backing <see cref="DependencyProperty"/> for the <see cref="Icon"/> property.
+        /// </summary>
+        public static readonly DependencyProperty IconProperty = DependencyProperty.Register(
+            nameof(Icon),
+            typeof(object),
+            typeof(FlyoutMenuButton),
+            new PropertyMetadata(defaultValue: null));
+
+        /// <summary>
+        /// Gets or sets the icon.
+        /// </summary>
+        public object Icon
+        {
+            get => (object)GetValue(IconProperty);
+            set => SetValue(IconProperty, value);
+        }
+
+        public FlyoutMenuButton()
+        {
+            this.DefaultStyleKey = typeof(FlyoutMenuButton);
+        }
+
+        protected override void OnApplyTemplate()
+        {
+            base.OnApplyTemplate();
+        }
+    }
+}