Refactor FlaxTests to run as Editor with all engine services initialized

Source/Engine/Tests/Tests.Build.cs

@@ -2,6 +2,7 @@
 
 using System.Collections.Generic;
 using Flax.Build;
+using Flax.Build.NativeCpp;
 
 /// <summary>
 /// Engine tests module.
@@ -14,6 +15,15 @@ public class Tests : EngineModule
         Deploy = false;
     }
 
+    /// <inheritdoc />
+    public override void Setup(BuildOptions options)
+    {
+        base.Setup(options);
+        
+        options.PrivateDependencies.Add("Content");
+        options.PrivateDependencies.Add("Level");
+    }
+
     /// <inheritdoc />
     public override void GetFilesToDeploy(List<string> files)
     {