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/Services/ProgressService.cs

@@ -0,0 +1,75 @@
+using CommunityToolkit.WinUI;
+using Ghost.Editor.Services.Contracts;
+using Microsoft.UI.Xaml;
+using Microsoft.UI.Xaml.Controls;
+using System.Runtime.CompilerServices;
+
+namespace Ghost.App.Services;
+
+public class ProgressService : IProgressService
+{
+    private Grid? _progressBarContainer;
+    private TextBlock? _progressMessage;
+    private ProgressBar? _progressBar;
+
+    [MethodImpl(MethodImplOptions.AggressiveInlining)]
+    private bool IsInitialized()
+    {
+        return _progressBarContainer != null && _progressMessage != null && _progressBar != null;
+    }
+
+    internal void SetReference(Grid progressBarContainer)
+    {
+        _progressBarContainer = progressBarContainer;
+        _progressMessage = _progressBarContainer.FindChild<TextBlock>();
+        _progressBar = _progressBarContainer.FindChild<ProgressBar>();
+    }
+
+    public void ShowProgress(string message, double progress = 0.0)
+    {
+        if (!IsInitialized())
+        {
+            return;
+        }
+
+        _progressBarContainer!.Visibility = Visibility.Visible;
+        _progressMessage!.Text = message;
+        _progressBar!.Value = progress;
+    }
+
+    public void ShowIndeterminateProgress(string message)
+    {
+        if (!IsInitialized())
+        {
+            return;
+        }
+
+        _progressBarContainer!.Visibility = Visibility.Visible;
+        _progressMessage!.Text = message;
+        _progressBar!.IsIndeterminate = true;
+    }
+
+    public void SetProgress(double progress)
+    {
+        _progressBar!.Value = progress;
+    }
+
+    public void HideProgress()
+    {
+        if (!IsInitialized())
+        {
+            return;
+        }
+
+        _progressBarContainer!.Visibility = Visibility.Collapsed;
+        _progressMessage!.Text = string.Empty;
+        _progressBar!.Value = 0.0;
+    }
+
+    internal void ClearReference()
+    {
+        _progressBarContainer = null;
+        _progressMessage = null;
+        _progressBar = null;
+    }
+}