Add support for compiling and running engine without C# scripting

(configurable via `EngineConfiguration.UseCSharp` in Flax.Build)

Source/Engine/Scripting/ManagedCLR/MStaticConverter.h

@@ -3,7 +3,9 @@
 #pragma once
 
 #include "Engine/Core/Types/String.h"
+#if USE_MONO
 #include <ThirdParty/mono-2.0/mono/metadata/mono-debug.h>
+#endif
 
 /// <summary>
 /// Class for converting mono classes and methods into usable form without instancing a class.
@@ -13,6 +15,7 @@ class MStaticConverter
 {
 public:
 
+#if USE_MONO
     static MonoClass* GetMonoClassFromObject(MonoObject* monoObject)
     {
         ASSERT(monoObject);
@@ -63,4 +66,5 @@ public:
         }
         return array;
     }
+#endif
 };