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/View/Windows/LandingWindow.xaml

@@ -0,0 +1,76 @@
+<?xml version="1.0" encoding="utf-8" ?>
+<winex:WindowEx
+    x:Class="Ghost.App.View.Windows.LandingWindow"
+    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
+    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
+    xmlns:behaviors="using:CommunityToolkit.WinUI.Behaviors"
+    xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
+    xmlns:interactivity="using:Microsoft.Xaml.Interactivity"
+    xmlns:local="using:Ghost.App.View.Windows"
+    xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
+    xmlns:winex="using:WinUIEx"
+    Activated="WindowEx_Activated"
+    Closed="WindowEx_Closed"
+    IsResizable="False"
+    mc:Ignorable="d">
+
+    <Window.SystemBackdrop>
+        <MicaBackdrop />
+    </Window.SystemBackdrop>
+
+    <Grid>
+        <Grid.RowDefinitions>
+            <RowDefinition Height="32" />
+            <RowDefinition Height="*" />
+        </Grid.RowDefinitions>
+
+        <Grid Grid.Row="0">
+            <TextBlock
+                Margin="24,0,0,0"
+                VerticalAlignment="Bottom"
+                Style="{StaticResource BodyTextBlockStyle}"
+                Text="Ghost Engine" />
+        </Grid>
+
+        <Grid Grid.Row="1" Padding="24,0,24,18">
+            <Grid.RowDefinitions>
+                <RowDefinition Height="Auto" />
+                <RowDefinition Height="*" />
+            </Grid.RowDefinitions>
+
+            <SelectorBar
+                Grid.Row="0"
+                HorizontalAlignment="Right"
+                SelectionChanged="SelectorBar_SelectionChanged">
+                <SelectorBarItem IsSelected="True" Text="Open">
+                    <SelectorBarItem.Icon>
+                        <FontIcon Glyph="&#xE838;" />
+                    </SelectorBarItem.Icon>
+                </SelectorBarItem>
+                <SelectorBarItem Text="Create">
+                    <SelectorBarItem.Icon>
+                        <FontIcon Glyph="&#xE8F4;" />
+                    </SelectorBarItem.Icon>
+                </SelectorBarItem>
+            </SelectorBar>
+
+            <Frame
+                x:Name="ContentFrame"
+                Grid.Row="1"
+                Padding="8"
+                CacheMode="BitmapCache"
+                CacheSize="10" />
+        </Grid>
+
+        <Grid Grid.Row="1" Padding="16">
+            <InfoBar
+                x:Name="InfoBar"
+                HorizontalAlignment="Right"
+                VerticalAlignment="Bottom">
+                <interactivity:Interaction.Behaviors>
+                    <behaviors:StackedNotificationsBehavior x:Name="NotificationQueue" />
+                </interactivity:Interaction.Behaviors>
+            </InfoBar>
+        </Grid>
+    </Grid>
+</winex:WindowEx>