Removed Ghost.ArcEntities project, it's replaced by Ghost.Entities

Added Playback to EntityCommandBuffer
Added JobSchedular to world
Added ISystem and SystemGroup
Updated packages

Ghost.Entities/Common.cs

@@ -0,0 +1,19 @@
+namespace Ghost.Entities;
+
+public readonly struct Time
+{
+    public int FrameCount
+    {
+        get; init;
+    }
+
+    public float DeltaTime
+    {
+        get; init;
+    }
+
+    public double ElapsedTime
+    {
+        get; init;
+    }
+}