Refactor project structure and enhance functionality

Changed the project namespace from `Ghost.Editor` to `Ghost.App` across multiple files.
Changed the `InternalsVisibleTo` attribute in `AssemblyInfo.cs` to include `Ghost.App`.
Changed the `ProjectRepository` class to add new asynchronous methods for retrieving projects by ID, name, and metadata path.
Changed the `ProjectService` class to utilize the new asynchronous project loading methods.
Changed the `SceneGraph` classes to improve node management and serialization.
Changed the `EntityManager` class to enhance entity management with new component handling methods.
Added new test classes, `EntityTest` and `SerializationTest`, to ensure reliability in entity and serialization systems.
Added the `Ghost.App` project file to establish a modular project structure.
Added the `Ghost.Generator` project for automated component serialization code generation.
Updated UI components to reflect the new namespace for proper functionality.

Ghost.Engine/Utilities/Utf8JsonWriterExtensions.cs

@@ -0,0 +1,40 @@
+using System.Text.Json;
+
+namespace Ghost.Engine.Utilities;
+
+public static class Utf8JsonWriterExtensions
+{
+    public static void WriteArray<T>(this Utf8JsonWriter writer, ReadOnlySpan<char> name, IEnumerable<T> source, Action<T> writeAction)
+    {
+        writer.WriteStartArray(name);
+        foreach (var item in source)
+        {
+            writeAction(item);
+        }
+        writer.WriteEndArray();
+    }
+
+    public static void WriteArray<T>(this Utf8JsonWriter writer, ReadOnlySpan<char> name, ReadOnlySpan<T> source, Action<T> writeAction)
+    {
+        writer.WriteStartArray(name);
+        foreach (var item in source)
+        {
+            writeAction(item);
+        }
+        writer.WriteEndArray();
+    }
+
+    public static void WriteObject(this Utf8JsonWriter writer, Action writeAction)
+    {
+        writer.WriteStartObject();
+        writeAction();
+        writer.WriteEndObject();
+    }
+
+    public static void WriteObject(this Utf8JsonWriter writer, ReadOnlySpan<char> name, Action writeAction)
+    {
+        writer.WriteStartObject(name);
+        writeAction();
+        writer.WriteEndObject();
+    }
+}