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/BasicInput/PropertyField.cs

@@ -0,0 +1,24 @@
+using Microsoft.UI.Xaml;
+using Microsoft.UI.Xaml.Controls;
+
+namespace Ghost.Editor.Controls;
+
+public sealed partial class PropertyField : ContentControl
+{
+    public string Label
+    {
+        get => (string)GetValue(LabelProperty);
+        set => SetValue(LabelProperty, value);
+    }
+
+    public static readonly DependencyProperty LabelProperty = DependencyProperty.Register(
+        nameof(Label),
+        typeof(string),
+        typeof(PropertyField),
+        new PropertyMetadata(default(string)));
+
+    public PropertyField()
+    {
+        DefaultStyleKey = typeof(PropertyField);
+    }
+}

Ghost.App/Controls/BasicInput/PropertyField.xaml

@@ -0,0 +1,33 @@
+<?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">
+
+    <Style TargetType="local:PropertyField">
+        <Setter Property="Template">
+            <Setter.Value>
+                <ControlTemplate TargetType="local:PropertyField">
+                    <Grid Height="32" Margin="2,4">
+                        <Grid.ColumnDefinitions>
+                            <ColumnDefinition Width="125" />
+                            <ColumnDefinition Width="*" />
+                        </Grid.ColumnDefinitions>
+                        <TextBlock
+                            Grid.Column="0"
+                            Margin="0,0,0,4"
+                            VerticalAlignment="Center"
+                            Style="{StaticResource BodyTextBlockStyle}"
+                            Text="{TemplateBinding Label}"
+                            TextTrimming="CharacterEllipsis" />
+
+                        <ContentPresenter
+                            Grid.Column="1"
+                            Content="{TemplateBinding Content}"
+                            ContentTemplate="{TemplateBinding ContentTemplate}" />
+                    </Grid>
+                </ControlTemplate>
+            </Setter.Value>
+        </Setter>
+    </Style>
+</ResourceDictionary>