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/Test/SerializationTest.cs

@@ -0,0 +1,51 @@
+using Ghost.Editor.SceneGraph;
+using Ghost.Entities;
+using Ghost.Test.TestFramework;
+using System.Text.Json;
+
+namespace Ghost.Test;
+
+internal class SerializationTest : ITest
+{
+    private const string _TEST_FILE_PATH = "C:/Users/Misaki/Downloads/testScene.ghostscene";
+
+    public void Run()
+    {
+        var testWorld = World.Create();
+        var entity1 = SceneGraphHelpers.CreateEntityNode(testWorld, "entity 1");
+        var entity2 = SceneGraphHelpers.CreateEntityNode(testWorld, "entity 2");
+        var entity3 = SceneGraphHelpers.CreateEntityNode(testWorld, "entity 3");
+        var entity4 = SceneGraphHelpers.CreateEntityNode(testWorld, "entity 4");
+        var entity5 = SceneGraphHelpers.CreateEntityNode(testWorld, "entity 5");
+
+        var testScene = new WorldNode(testWorld, "Test Scene");
+
+        testWorld.SystemStorage.AddSystem<TestSystem>();
+
+        SceneGraphHelpers.AttachChild(testScene, entity1, entity2);
+        SceneGraphHelpers.AttachChild(testScene, entity1, entity3);
+        SceneGraphHelpers.AttachChild(testScene, entity2, entity4);
+
+        testScene.AddChild(entity1);
+        testScene.AddChild(entity5);
+
+        var createStream = new FileStream(_TEST_FILE_PATH, FileMode.Create, FileAccess.Write, FileShare.None);
+
+        var options = new JsonSerializerOptions
+        {
+            WriteIndented = true,
+            IncludeFields = true,
+            IgnoreReadOnlyProperties = true,
+        };
+
+        JsonSerializer.Serialize(createStream, testScene, options);
+
+        createStream.Dispose();
+        testWorld.Dispose();
+
+        var readStream = new FileStream(_TEST_FILE_PATH, FileMode.Open, FileAccess.Read, FileShare.Read);
+
+        var deserializedScene = JsonSerializer.Deserialize<WorldNode>(readStream, options) ?? throw new Exception("Deserialization failed.");
+        deserializedScene.LoadAsync();
+    }
+}