Refactor application structure and add unit tests

Added:
- New `ProgressService` class for managing progress indicators.
- New `AssetDatabase`, `AssetOpenHandlerAttribute`, and `AsyncAssetOpenHandlerAttribute` classes for asset handling.
- `Ghost.UnitTest` project for unit testing with associated files and configurations.

Changed:
- `ActivationHandler` class to ensure correct handling of `LaunchActivatedEventArgs`.
- `App.xaml.cs` to register `INotificationService` and `IProgressService`, replacing `StackedNotificationService`.
- `OnLaunched` method in `App.xaml.cs` to correctly call `ActivationHandler.Handle(args)` and start the host.
- `INavigationAware` interface from internal to public for broader access.
- `EditorState.cs` to activate `EditorApplication` with the current service provider.
- Property names in `AssetItem` and `ExplorerItem` structs to `Name` and `FullName`.
- `NotificationService` class to implement `INotificationService` and refactor notification handling.
- `AssetPathToGlyphConverter` to handle file extensions consistently.
- Bindings in `ProjectPage.xaml` and `ProjectPage.xaml.cs` to use `FullName` instead of `Path`.
- `EngineEditorWindow` and `LandingWindow` classes to utilize new notification and progress services.
- `Logger` class to include a new method for logging errors with exceptions.

Updated:
- Manifest files and project files to reflect new structure and dependencies.
- Solution file `GhostEngine.sln` to include the new unit test project.
- Added several new test classes and methods in `UnitTests.cs`.

Ghost.App/Controls/Internal/InspectorView.cs

@@ -0,0 +1,24 @@
+using Microsoft.UI.Xaml;
+using Microsoft.UI.Xaml.Controls;
+
+namespace Ghost.Editor.Controls.Internal;
+
+internal sealed partial class InspectorView : ContentControl
+{
+    public UIElement? Header
+    {
+        get => (UIElement)GetValue(HeaderProperty);
+        set => SetValue(HeaderProperty, value);
+    }
+
+    public static readonly DependencyProperty HeaderProperty = DependencyProperty.Register(
+        nameof(Header),
+        typeof(UIElement),
+        typeof(InspectorView),
+        new PropertyMetadata(null));
+
+    public InspectorView()
+    {
+        DefaultStyleKey = typeof(InspectorView);
+    }
+}

Ghost.App/Controls/Internal/InspectorView.xaml

@@ -0,0 +1,41 @@
+<?xml version="1.0" encoding="utf-8" ?>
+<ResourceDictionary
+    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
+    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
+    xmlns:local="using:Ghost.Editor.Controls.Internal">
+    <Style TargetType="local:InspectorView">
+        <Setter Property="Template">
+            <Setter.Value>
+                <ControlTemplate TargetType="local:InspectorView">
+                    <Grid>
+                        <Grid.RowDefinitions>
+                            <RowDefinition Height="50" />
+                            <RowDefinition Height="*" />
+                        </Grid.RowDefinitions>
+
+                        <!--  Header  -->
+                        <Grid Grid.Row="0">
+                            <ContentPresenter
+                                HorizontalAlignment="Stretch"
+                                VerticalAlignment="Stretch"
+                                Content="{TemplateBinding Header}"
+                                ContentTemplate="{TemplateBinding HeaderTemplate}" />
+                        </Grid>
+
+                        <!--  Content  -->
+                        <Grid Grid.Row="1">
+                            <ScrollViewer HorizontalScrollBarVisibility="Auto" VerticalScrollBarVisibility="Auto">
+                                <ContentPresenter
+                                    HorizontalAlignment="Stretch"
+                                    VerticalAlignment="Stretch"
+                                    Content="{TemplateBinding Content}"
+                                    ContentTemplate="{TemplateBinding ContentTemplate}"
+                                    ContentTransitions="{TemplateBinding ContentTransitions}" />
+                            </ScrollViewer>
+                        </Grid>
+                    </Grid>
+                </ControlTemplate>
+            </Setter.Value>
+        </Setter>
+    </Style>
+</ResourceDictionary>

Ghost.App/Controls/Internal/InternalControls.xaml

@@ -0,0 +1,4 @@
+<?xml version="1.0" encoding="utf-8" ?>
+<ResourceDictionary xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml">
+    <ResourceDictionary.MergedDictionaries />
+</ResourceDictionary>