Use script instance binding for objects constructed from C#

Only possible if the object class is a "native type". If the object class is a user class (that derives a "native type") then a script is needed.
Since CSharpLanguage does cleanup of script instance bindings when finished, cases like #25621 will no longer cause problems.

Fixed ~Object() trying to free script instance bindings after the language has already been removed, which would result in a NULL dereference.

modules/mono/editor/bindings_generator.cpp

@@ -849,6 +849,8 @@ Error BindingsGenerator::_generate_cs_type(const TypeInterface &itype, const Str
 		}
 	}
 
+	// TODO: BINDINGS_NATIVE_NAME_FIELD should be StringName, once we support it in C#
+
 	if (itype.is_singleton) {
 		// Add the type name and the singleton pointer as static fields