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.UnitTest/UnitTests.cs

@@ -0,0 +1,25 @@
+using Microsoft.UI.Xaml.Controls;
+using Microsoft.VisualStudio.TestTools.UnitTesting;
+using Microsoft.VisualStudio.TestTools.UnitTesting.AppContainer;
+using System;
+using System.Collections.Generic;
+using System.Linq;
+
+namespace Ghost.UnitTest;
+[TestClass]
+public partial class UnitTest1
+{
+    [TestMethod]
+    public void TestMethod1()
+    {
+        Assert.AreEqual(0, 0);
+    }
+
+    // Use the UITestMethod attribute for tests that need to run on the UI thread.
+    [UITestMethod]
+    public void TestMethod2()
+    {
+        var grid = new Grid();
+        Assert.AreEqual(0, grid.MinWidth);
+    }
+}